Capitalized software development costs in progress associated with future releases.

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- Definition

Summary of Significant Accounting Policies [Line Items]

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic net Income or Loss per outstanding limited partnership unit in the future and that were not included in the computation of diluted net income per limited partnership unit, because to do so would increase net income per unit amounts or decrease loss per unit amounts for the period presented.

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- Definition

Additions made to capitalized computer software costs during the period.

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Amount of expense for amortization of capitalized computer software costs.

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- Definition

The carrying amount of capitalized computer software costs net of accumulated amortization as of the balance sheet date.

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Amount of cash and cash equivalent. Cash includes, but is not limited to, currency on hand, demand deposit with financial institution, and account with general characteristic of demand deposit. Cash equivalent includes, but is not limited to, short-term, highly liquid investment that is both readily convertible to known amount of cash and so near maturity that it presents insignificant risk of change in value because of change in interest rate.

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Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount of financial support provided to a nonconsolidated legal entity that is required to comply with or operate in accordance with requirements that are similar to those included in Rule 2a-7 of the Investment Company Act of 1940 for registered money market funds.

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Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025
Summary of Significant Accounting Policies [Line Items]
Capitalized software development costs	$ 5,546	$ 7,362
Net book value of capitalized software	$ 230,746		$ 234,272
Anti-dilutive employee stock options (in shares)	4,426	5,834
Anti-dilutive employee stock options (in USD per share)	$ 75.27	$ 65.95
Investment Managers
Summary of Significant Accounting Policies [Line Items]
Capitalized software development costs	$ 1,574	$ 2,987
Capitalized software in progress	1,574
SEI Wealth Platform
Summary of Significant Accounting Policies [Line Items]
Capitalized software development costs	3,972	4,375
Net book value of capitalized software	190,654
Capitalized software in progress	3,972
Amortization expense related to the SEI Wealth Platform	$ 7,564	7,099
SEI Wealth Platform \| Weighted Average
Summary of Significant Accounting Policies [Line Items]
Estimated useful life of the SEI Wealth Platform	7 years 4 months 24 days
Investment Managers Platform
Summary of Significant Accounting Policies [Line Items]
Net book value of capitalized software	$ 40,092
Estimated useful life of the SEI Wealth Platform	6 years 4 months 24 days
Amortization expense related to the SEI Wealth Platform	$ 1,508
SEI-Sponsored Open-Ended Money Market Mutual Funds
Summary of Significant Accounting Policies [Line Items]
Cash and cash equivalents invested in SEI-sponsored money market funds	73,254		$ 201,675
SEI-Sponsored Open-Ended Money Market Mutual Funds
Summary of Significant Accounting Policies [Line Items]
Fees waived	$ 5,077	$ 4,133