v3.26.1
Shareholder Report, Average Annual Return (Details)
 12 Months Ended 31 Months Ended 60 Months Ended 120 Months Ended
May 31, 2026
May 31, 2026
May 31, 2026
May 31, 2026
Without Sales Load [Member] | C000005503        
Average Annual Return [Line Items]        
Average Annual Return, Percent 14.76%   5.28% 7.41%
Without Sales Load [Member] | C000049238        
Average Annual Return [Line Items]        
Average Annual Return, Percent 14.48%   5.01% 7.14%
Without Sales Load [Member] | C000049239        
Average Annual Return [Line Items]        
Average Annual Return, Percent 14.28%   4.75% 6.88%
Without Sales Load [Member] | C000244826        
Average Annual Return [Line Items]        
Average Annual Return, Percent 14.98% 13.76%    
Bloomberg U.S. Aggregate Bond Index        
Average Annual Return [Line Items]        
Average Annual Return, Percent 5.13%   0.17% 1.70%
Bloomberg U.S. Aggregate Bond Index        
Average Annual Return [Line Items]        
Average Annual Return, Percent 5.13%   0.17% 1.70%
Bloomberg U.S. Aggregate Bond Index        
Average Annual Return [Line Items]        
Average Annual Return, Percent 5.13%   0.17% 1.70%
Bloomberg U.S. Aggregate Bond Index        
Average Annual Return [Line Items]        
Average Annual Return, Percent 5.13% 6.00%    
S&P Target Date 2015 Index        
Average Annual Return [Line Items]        
Average Annual Return, Percent 13.81%   5.10% 6.55%
S&P Target Date 2015 Index        
Average Annual Return [Line Items]        
Average Annual Return, Percent 13.81%   5.10% 6.55%
S&P Target Date 2015 Index        
Average Annual Return [Line Items]        
Average Annual Return, Percent 13.81%   5.10% 6.55%
S&P Target Date 2015 Index        
Average Annual Return [Line Items]        
Average Annual Return, Percent 13.81% 12.52%