v3.25.4
Shareholder Report, Average Annual Return (Details)
 12 Months Ended 60 Months Ended 120 Months Ended
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Royce Capital Fund - Micro-Cap Portfolio - Investment Class      
Average Annual Return [Line Items]      
Average Annual Return, Percent 13.89% 9.17% 10.14%
Royce Capital Fund - Micro-Cap Portfolio - Service Class      
Average Annual Return [Line Items]      
Average Annual Return, Percent 13.58% 8.85% 9.86%
Royce Capital Fund-Small-Cap Portfolio - Investment Class      
Average Annual Return [Line Items]      
Average Annual Return, Percent 8.93% 10.66% 7.88%
Royce Capital Fund-Small-Cap Portfolio - Service Class      
Average Annual Return [Line Items]      
Average Annual Return, Percent 8.73% 10.40% 7.63%
Russell 3000 Index One      
Average Annual Return [Line Items]      
Average Annual Return, Percent 17.15% 13.15% 14.29%
Russell Microcap Index One      
Average Annual Return [Line Items]      
Average Annual Return, Percent 22.98% 7.32% 9.58%
Russell 2000 Index One      
Average Annual Return [Line Items]      
Average Annual Return, Percent 12.81% 6.09% 9.62%
Russell3000 Index Two      
Average Annual Return [Line Items]      
Average Annual Return, Percent 17.15% 13.15% 14.29%
Russell Microcap Index Two      
Average Annual Return [Line Items]      
Average Annual Return, Percent 22.98% 7.32% 9.58%
Russell2000 Index Two      
Average Annual Return [Line Items]      
Average Annual Return, Percent 12.81% 6.09% 9.62%
Russell3000 Index Three      
Average Annual Return [Line Items]      
Average Annual Return, Percent 17.15% 13.15% 14.29%
Russell 2000 Value Index One      
Average Annual Return [Line Items]      
Average Annual Return, Percent 12.59% 8.88% 9.27%
Russell2000 Index Three      
Average Annual Return [Line Items]      
Average Annual Return, Percent 12.81% 6.09% 9.62%
Russell 3000 Index Four      
Average Annual Return [Line Items]      
Average Annual Return, Percent 17.15% 13.15% 14.29%
Russell 2000 Value Index Two      
Average Annual Return [Line Items]      
Average Annual Return, Percent 12.59% 8.88% 9.27%
Russell 2000 Index Four      
Average Annual Return [Line Items]      
Average Annual Return, Percent 12.81% 6.09% 9.62%