v3.26.1
Shareholder Report, Average Annual Return (Details)
 12 Months Ended 60 Months Ended 120 Months Ended
May 31, 2026
May 31, 2026
May 31, 2026
Without Sales Load [Member] | C000129662      
Average Annual Return [Line Items]      
Average Annual Return, Percent 12.37% 4.38% 6.34%
Without Sales Load [Member] | C000129663      
Average Annual Return [Line Items]      
Average Annual Return, Percent 12.15% 4.12% 6.06%
Without Sales Load [Member] | C000169042      
Average Annual Return [Line Items]      
Average Annual Return, Percent 12.57% 4.54% 6.47%
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%
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%