v3.26.1
Shareholder Report, Average Annual Return (Details)
 12 Months Ended 60 Months Ended 120 Months Ended
Apr. 30, 2026
Apr. 30, 2026
Apr. 30, 2026
C000005790      
Average Annual Return [Line Items]      
Average Annual Return, Percent 14.98% 4.11% 7.01%
C000005792      
Average Annual Return [Line Items]      
Average Annual Return, Percent 19.37% 4.41% 6.93%
Without Sales Load [Member] | C000172904      
Average Annual Return [Line Items]      
Average Annual Return, Percent 21.76% 5.60% 7.95%
Without Sales Load [Member] | C000005794      
Average Annual Return [Line Items]      
Average Annual Return, Percent 20.91% 4.86% 7.21%
Without Sales Load [Member] | C000005793      
Average Annual Return [Line Items]      
Average Annual Return, Percent 21.62% 5.50% 7.86%
Without Sales Load [Member] | C000005790      
Average Annual Return [Line Items]      
Average Annual Return, Percent 21.35% 5.24% 7.59%
Without Sales Load [Member] | C000005792      
Average Annual Return [Line Items]      
Average Annual Return, Percent 20.37% 4.41% 6.93%
FTSE World Index      
Average Annual Return [Line Items]      
Average Annual Return, Percent 33.25% 12.04% 13.27%
FTSE World Index      
Average Annual Return [Line Items]      
Average Annual Return, Percent 33.25% 12.04% 13.27%
FTSE World Index      
Average Annual Return [Line Items]      
Average Annual Return, Percent 33.25% 12.04% 13.27%
FTSE World Index      
Average Annual Return [Line Items]      
Average Annual Return, Percent 33.25% 12.04% 13.27%
FTSE World Index      
Average Annual Return [Line Items]      
Average Annual Return, Percent 33.25% 12.04% 13.27%
Reference Benchmark      
Average Annual Return [Line Items]      
Line Graph and Table Measure Name Reference Benchmark    
Average Annual Return, Percent 20.50% 6.77% 8.23%
Reference Benchmark      
Average Annual Return [Line Items]      
Line Graph and Table Measure Name Reference Benchmark    
Average Annual Return, Percent 20.50% 6.77% 8.23%
Reference Benchmark      
Average Annual Return [Line Items]      
Line Graph and Table Measure Name Reference Benchmark    
Average Annual Return, Percent 20.50% 6.77% 8.23%
Reference Benchmark      
Average Annual Return [Line Items]      
Line Graph and Table Measure Name Reference Benchmark    
Average Annual Return, Percent 20.50% 6.77% 8.23%
Reference Benchmark      
Average Annual Return [Line Items]      
Line Graph and Table Measure Name Reference Benchmark    
Average Annual Return, Percent 20.50% 6.77% 8.23%