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State Street Moderate ETF Portfolio Average Annual Total Returns
12 Months Ended 60 Months Ended 120 Months Ended
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
MSCI All Country World Index (reflects no deduction for mutual fund fees or expenses)[Member]      
Prospectus [Line Items]      
Average Annual Return, Percent 22.34% 11.19% 11.72%
State Street Moderate Composite Index (reflects no deduction for mutual fund fees or expenses)[Member]      
Prospectus [Line Items]      
Average Annual Return, Percent 16.05% 7.04% 8.28%
Class A      
Prospectus [Line Items]      
Average Annual Return, Percent 17.09% 7.46% 8.13%
Class B      
Prospectus [Line Items]      
Average Annual Return, Percent 16.78% 7.19% 7.85%
Class E      
Prospectus [Line Items]      
Average Annual Return, Percent 16.93% 7.30% 7.96%