v3.26.1
Shareholder Report
 6 Months Ended
Feb. 28, 2026
USD ($)
$ / shares
Shareholder Report [Line Items]  
Document Type N-CSRS
Amendment Flag false
Registrant Name Putnam Asset Allocation Funds
Entity Central Index Key 0000914209
Entity Investment Company Type N-1A
Document Period End Date Feb. 28, 2026
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Class A  
Shareholder Report [Line Items]  
Fund Name Putnam Multi-Asset Income Fund
Class Name Class A
Trading Symbol PMIAX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Putnam Multi-Asset Income Fund for the period September 1, 2025, to February 28, 2026.
Additional Information [Text Block] You can find additional information about the Fund at https://www.franklintempleton.com/regulatory-fund-documents. You can also request this information by contacting us at (800) 225-1581.
Additional Information Phone Number (800) 225-1581
Additional Information Website https://www.franklintempleton.com/regulatory-fund-documents
Expenses [Text Block]
WHAT WERE THE FUND COSTS FOR THE LAST SIX MONTHS? (based on a hypothetical $10,000 investment)
Class Name
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment*,†
Class A
$41
0.80%
[1],[2]
Expenses Paid, Amount $ 41
Expense Ratio, Percent 0.80%
Net Assets $ 861,093,537
Holdings Count | $ / shares 1,862
Investment Company Portfolio Turnover 53.00%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (as of February 28, 2026)
Total Net Assets
$861,093,537
Total Number of Portfolio Holdings (excludes derivatives, except purchased options, if any)
1,862
Portfolio Turnover Rate
53%
Holdings [Text Block]
WHAT DID THE FUND INVEST IN? (as of February 28, 2026)
Portfolio Composition† (% of Total Net Assets)
image
 [3],[4]
Updated Prospectus Web Address https://www.franklintempleton.com/regulatory-fund-documents
Class C  
Shareholder Report [Line Items]  
Fund Name Putnam Multi-Asset Income Fund
Class Name Class C
Trading Symbol PMICX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Putnam Multi-Asset Income Fund for the period September 1, 2025, to February 28, 2026.
Additional Information [Text Block] You can find additional information about the Fund at https://www.franklintempleton.com/regulatory-fund-documents. You can also request this information by contacting us at (800) 225-1581.
Additional Information Phone Number (800) 225-1581
Additional Information Website https://www.franklintempleton.com/regulatory-fund-documents
Expenses [Text Block]
WHAT WERE THE FUND COSTS FOR THE LAST SIX MONTHS? (based on a hypothetical $10,000 investment)
Class Name
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment*,†
Class C
$79
1.55%
[5],[6]
Expenses Paid, Amount $ 79
Expense Ratio, Percent 1.55%
Net Assets $ 861,093,537
Holdings Count | $ / shares 1,862
Investment Company Portfolio Turnover 53.00%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (as of February 28, 2026)
Total Net Assets
$861,093,537
Total Number of Portfolio Holdings (excludes derivatives, except purchased options, if any)
1,862
Portfolio Turnover Rate
53%
Holdings [Text Block]
WHAT DID THE FUND INVEST IN? (as of February 28, 2026)
Portfolio Composition† (% of Total Net Assets)
image
 [7],[8]
Updated Prospectus Web Address https://www.franklintempleton.com/regulatory-fund-documents
Class P  
Shareholder Report [Line Items]  
Fund Name Putnam Multi-Asset Income Fund
Class Name Class P
No Trading Symbol true
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Putnam Multi-Asset Income Fund for the period September 1, 2025, to February 28, 2026.
Additional Information [Text Block] You can find additional information about the Fund at https://www.franklintempleton.com/regulatory-fund-documents. You can also request this information by contacting us at (800) 225-1581.
Additional Information Phone Number (800) 225-1581
Additional Information Website https://www.franklintempleton.com/regulatory-fund-documents
Expenses [Text Block]
WHAT WERE THE FUND COSTS FOR THE LAST SIX MONTHS? (based on a hypothetical $10,000 investment)
Class Name
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment*,†
Class P
$22
0.42%
[9],[10]
Expenses Paid, Amount $ 22
Expense Ratio, Percent 0.42%
Net Assets $ 861,093,537
Holdings Count | $ / shares 1,862
Investment Company Portfolio Turnover 53.00%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (as of February 28, 2026)
Total Net Assets
$861,093,537
Total Number of Portfolio Holdings (excludes derivatives, except purchased options, if any)
1,862
Portfolio Turnover Rate
53%
Holdings [Text Block]
WHAT DID THE FUND INVEST IN? (as of February 28, 2026)
Portfolio Composition† (% of Total Net Assets)
image
 [11],[12]
Updated Prospectus Web Address https://www.franklintempleton.com/regulatory-fund-documents
Class R  
Shareholder Report [Line Items]  
Fund Name Putnam Multi-Asset Income Fund
Class Name Class R
Trading Symbol PMIRX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Putnam Multi-Asset Income Fund for the period September 1, 2025, to February 28, 2026.
Additional Information [Text Block] You can find additional information about the Fund at https://www.franklintempleton.com/regulatory-fund-documents. You can also request this information by contacting us at (800) 225-1581.
Additional Information Phone Number (800) 225-1581
Additional Information Website https://www.franklintempleton.com/regulatory-fund-documents
Expenses [Text Block]
WHAT WERE THE FUND COSTS FOR THE LAST SIX MONTHS? (based on a hypothetical $10,000 investment)
Class Name
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment*,†
Class R
$54
1.05%
[13],[14]
Expenses Paid, Amount $ 54
Expense Ratio, Percent 1.05%
Net Assets $ 861,093,537
Holdings Count | $ / shares 1,862
Investment Company Portfolio Turnover 53.00%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (as of February 28, 2026)
Total Net Assets
$861,093,537
Total Number of Portfolio Holdings (excludes derivatives, except purchased options, if any)
1,862
Portfolio Turnover Rate
53%
Holdings [Text Block]
WHAT DID THE FUND INVEST IN? (as of February 28, 2026)
Portfolio Composition† (% of Total Net Assets)
image
 [15],[16]
Updated Prospectus Web Address https://www.franklintempleton.com/regulatory-fund-documents
Class R5  
Shareholder Report [Line Items]  
Fund Name Putnam Multi-Asset Income Fund
Class Name Class R5
Trading Symbol PMILX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Putnam Multi-Asset Income Fund for the period September 1, 2025, to February 28, 2026.
Additional Information [Text Block] You can find additional information about the Fund at https://www.franklintempleton.com/regulatory-fund-documents. You can also request this information by contacting us at (800) 225-1581.
Additional Information Phone Number (800) 225-1581
Additional Information Website https://www.franklintempleton.com/regulatory-fund-documents
Expenses [Text Block]
WHAT WERE THE FUND COSTS FOR THE LAST SIX MONTHS? (based on a hypothetical $10,000 investment)
Class Name
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment*,†
Class R5
$28
0.55%
[17],[18]
Expenses Paid, Amount $ 28
Expense Ratio, Percent 0.55%
Net Assets $ 861,093,537
Holdings Count | $ / shares 1,862
Investment Company Portfolio Turnover 53.00%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (as of February 28, 2026)
Total Net Assets
$861,093,537
Total Number of Portfolio Holdings (excludes derivatives, except purchased options, if any)
1,862
Portfolio Turnover Rate
53%
Holdings [Text Block]
WHAT DID THE FUND INVEST IN? (as of February 28, 2026)
Portfolio Composition† (% of Total Net Assets)
image
 [19],[20]
Updated Prospectus Web Address https://www.franklintempleton.com/regulatory-fund-documents
Class R6  
Shareholder Report [Line Items]  
Fund Name Putnam Multi-Asset Income Fund
Class Name Class R6
Trading Symbol PMIVX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Putnam Multi-Asset Income Fund for the period September 1, 2025, to February 28, 2026.
Additional Information [Text Block] You can find additional information about the Fund at https://www.franklintempleton.com/regulatory-fund-documents. You can also request this information by contacting us at (800) 225-1581.
Additional Information Phone Number (800) 225-1581
Additional Information Website https://www.franklintempleton.com/regulatory-fund-documents
Expenses [Text Block]
WHAT WERE THE FUND COSTS FOR THE LAST SIX MONTHS? (based on a hypothetical $10,000 investment)
Class Name
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment*,†
Class R6
$24
0.46%
[21],[22]
Expenses Paid, Amount $ 24
Expense Ratio, Percent 0.46%
Net Assets $ 861,093,537
Holdings Count | $ / shares 1,862
Investment Company Portfolio Turnover 53.00%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (as of February 28, 2026)
Total Net Assets
$861,093,537
Total Number of Portfolio Holdings (excludes derivatives, except purchased options, if any)
1,862
Portfolio Turnover Rate
53%
Holdings [Text Block]
WHAT DID THE FUND INVEST IN? (as of February 28, 2026)
Portfolio Composition† (% of Total Net Assets)
image
 [23],[24]
Updated Prospectus Web Address https://www.franklintempleton.com/regulatory-fund-documents
Class Y  
Shareholder Report [Line Items]  
Fund Name Putnam Multi-Asset Income Fund
Class Name Class Y
Trading Symbol PMIYX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Putnam Multi-Asset Income Fund for the period September 1, 2025, to February 28, 2026.
Additional Information [Text Block] You can find additional information about the Fund at https://www.franklintempleton.com/regulatory-fund-documents. You can also request this information by contacting us at (800) 225-1581.
Additional Information Phone Number (800) 225-1581
Additional Information Website https://www.franklintempleton.com/regulatory-fund-documents
Expenses [Text Block]
WHAT WERE THE FUND COSTS FOR THE LAST SIX MONTHS? (based on a hypothetical $10,000 investment)
Class Name
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment*,†
Class Y
$28
0.55%
[25],[26]
Expenses Paid, Amount $ 28
Expense Ratio, Percent 0.55%
Net Assets $ 861,093,537
Holdings Count | $ / shares 1,862
Investment Company Portfolio Turnover 53.00%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (as of February 28, 2026)
Total Net Assets
$861,093,537
Total Number of Portfolio Holdings (excludes derivatives, except purchased options, if any)
1,862
Portfolio Turnover Rate
53%
Holdings [Text Block]
WHAT DID THE FUND INVEST IN? (as of February 28, 2026)
Portfolio Composition† (% of Total Net Assets)
image
 [27],[28]
Updated Prospectus Web Address https://www.franklintempleton.com/regulatory-fund-documents
[1]
* Reflects fee waivers and/or expense reimbursements, without which expenses would have been higher.
[2]
† Annualized.
[3]
U.S. Money Markets, if any, represent the market value weights of cash, short-term securities, and derivative notional offsets in the portfolio. Holdings and allocations may vary over time.
[4]
† Certain categories may represent less than 0.1%.
[5]
* Reflects fee waivers and/or expense reimbursements, without which expenses would have been higher.
[6]
† Annualized.
[7]
U.S. Money Markets, if any, represent the market value weights of cash, short-term securities, and derivative notional offsets in the portfolio. Holdings and allocations may vary over time.
[8]
† Certain categories may represent less than 0.1%.
[9]
* Reflects fee waivers and/or expense reimbursements, without which expenses would have been higher.
[10]
† Annualized.
[11]
U.S. Money Markets, if any, represent the market value weights of cash, short-term securities, and derivative notional offsets in the portfolio. Holdings and allocations may vary over time.
[12]
† Certain categories may represent less than 0.1%.
[13]
* Reflects fee waivers and/or expense reimbursements, without which expenses would have been higher.
[14]
† Annualized.
[15]
U.S. Money Markets, if any, represent the market value weights of cash, short-term securities, and derivative notional offsets in the portfolio. Holdings and allocations may vary over time.
[16]
† Certain categories may represent less than 0.1%.
[17]
* Reflects fee waivers and/or expense reimbursements, without which expenses would have been higher.
[18]
† Annualized.
[19]
U.S. Money Markets, if any, represent the market value weights of cash, short-term securities, and derivative notional offsets in the portfolio. Holdings and allocations may vary over time.
[20]
† Certain categories may represent less than 0.1%.
[21]
* Reflects fee waivers and/or expense reimbursements, without which expenses would have been higher.
[22]
† Annualized.
[23]
U.S. Money Markets, if any, represent the market value weights of cash, short-term securities, and derivative notional offsets in the portfolio. Holdings and allocations may vary over time.
[24]
† Certain categories may represent less than 0.1%.
[25]
* Reflects fee waivers and/or expense reimbursements, without which expenses would have been higher.
[26]
† Annualized.
[27]
U.S. Money Markets, if any, represent the market value weights of cash, short-term securities, and derivative notional offsets in the portfolio. Holdings and allocations may vary over time.
[28]
† Certain categories may represent less than 0.1%.