Shareholder Report, Holdings (Details)	Jun. 30, 2026
Royce Capital Fund - Micro-Cap Portfolio - Investment Class \| Ultra Clean Holdings [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.70%
Royce Capital Fund - Micro-Cap Portfolio - Investment Class \| Ichor Holdings [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.70%
Royce Capital Fund - Micro-Cap Portfolio - Investment Class \| Graham Corporation [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.50%
Royce Capital Fund - Micro-Cap Portfolio - Investment Class \| NWPX Infrastructure [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.50%
Royce Capital Fund - Micro-Cap Portfolio - Investment Class \| Cohu [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.40%
Royce Capital Fund - Micro-Cap Portfolio - Investment Class \| Lincoln Educational Services
Holdings [Line Items]
Percent of Net Asset Value	1.40%
Royce Capital Fund - Micro-Cap Portfolio - Investment Class \| Bel Fuse Cl. B [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.40%
Royce Capital Fund - Micro-Cap Portfolio - Investment Class \| EZCORP Cl. A [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.30%
Royce Capital Fund - Micro-Cap Portfolio - Investment Class \| Lindblad Expeditions Holdings [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.30%
Royce Capital Fund - Micro-Cap Portfolio - Investment Class \| Digi International [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.20%
Royce Capital Fund - Micro-Cap Portfolio - Investment Class \| Industrial Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	25.30%
Royce Capital Fund - Micro-Cap Portfolio - Investment Class \| Information Technology Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	23.50%
Royce Capital Fund - Micro-Cap Portfolio - Investment Class \| Healthcare Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	12.40%
Royce Capital Fund - Micro-Cap Portfolio - Investment Class \| Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	11.90%
Royce Capital Fund - Micro-Cap Portfolio - Investment Class \| Financial Services Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	11.60%
Royce Capital Fund - Micro-Cap Portfolio - Investment Class \| Materials Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	4.10%
Royce Capital Fund - Micro-Cap Portfolio - Investment Class \| Energy Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	3.50%
Royce Capital Fund - Micro-Cap Portfolio - Investment Class \| Communications Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.00%
Royce Capital Fund - Micro-Cap Portfolio - Investment Class \| Real Estate Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.60%
Royce Capital Fund - Micro-Cap Portfolio - Investment Class \| Cash and Cash Equivalents [Member]
Holdings [Line Items]
Percent of Net Asset Value	5.10%
Royce Capital Fund - Micro-Cap Portfolio - Service Class \| Ultra Clean Holdings [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.70%
Royce Capital Fund - Micro-Cap Portfolio - Service Class \| Ichor Holdings [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.70%
Royce Capital Fund - Micro-Cap Portfolio - Service Class \| Graham Corporation [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.50%
Royce Capital Fund - Micro-Cap Portfolio - Service Class \| NWPX Infrastructure [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.50%
Royce Capital Fund - Micro-Cap Portfolio - Service Class \| Cohu [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.40%
Royce Capital Fund - Micro-Cap Portfolio - Service Class \| Lincoln Educational Services
Holdings [Line Items]
Percent of Net Asset Value	1.40%
Royce Capital Fund - Micro-Cap Portfolio - Service Class \| Bel Fuse Cl. B [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.40%
Royce Capital Fund - Micro-Cap Portfolio - Service Class \| EZCORP Cl. A [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.30%
Royce Capital Fund - Micro-Cap Portfolio - Service Class \| Lindblad Expeditions Holdings [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.30%
Royce Capital Fund - Micro-Cap Portfolio - Service Class \| Digi International [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.20%
Royce Capital Fund - Micro-Cap Portfolio - Service Class \| Industrial Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	25.30%
Royce Capital Fund - Micro-Cap Portfolio - Service Class \| Information Technology Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	23.50%
Royce Capital Fund - Micro-Cap Portfolio - Service Class \| Healthcare Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	12.40%
Royce Capital Fund - Micro-Cap Portfolio - Service Class \| Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	11.90%
Royce Capital Fund - Micro-Cap Portfolio - Service Class \| Financial Services Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	11.60%
Royce Capital Fund - Micro-Cap Portfolio - Service Class \| Materials Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	4.10%
Royce Capital Fund - Micro-Cap Portfolio - Service Class \| Energy Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	3.50%
Royce Capital Fund - Micro-Cap Portfolio - Service Class \| Communications Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.00%
Royce Capital Fund - Micro-Cap Portfolio - Service Class \| Real Estate Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.60%
Royce Capital Fund - Micro-Cap Portfolio - Service Class \| Cash and Cash Equivalents [Member]
Holdings [Line Items]
Percent of Net Asset Value	5.10%
Royce Capital Fund-Small-Cap Portfolio - Investment Class \| TD SYNNEX [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.70%
Royce Capital Fund-Small-Cap Portfolio - Investment Class \| M/I Homes [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.40%
Royce Capital Fund-Small-Cap Portfolio - Investment Class \| Blue Bird [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.30%
Royce Capital Fund-Small-Cap Portfolio - Investment Class \| Diebold Nixdorf [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.20%
Royce Capital Fund-Small-Cap Portfolio - Investment Class \| Timberland Bancorp [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.00%
Royce Capital Fund-Small-Cap Portfolio - Investment Class \| Village Super Market Cl. A [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.00%
Royce Capital Fund-Small-Cap Portfolio - Investment Class \| IBEX [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.00%
Royce Capital Fund-Small-Cap Portfolio - Investment Class \| Interface [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.00%
Royce Capital Fund-Small-Cap Portfolio - Investment Class \| PulteGroup [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.00%
Royce Capital Fund-Small-Cap Portfolio - Investment Class \| Unity Bancorp [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.80%
Royce Capital Fund-Small-Cap Portfolio - Investment Class \| Industrial Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	16.90%
Royce Capital Fund-Small-Cap Portfolio - Investment Class \| Information Technology Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	14.20%
Royce Capital Fund-Small-Cap Portfolio - Investment Class \| Healthcare Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	8.70%
Royce Capital Fund-Small-Cap Portfolio - Investment Class \| Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	22.60%
Royce Capital Fund-Small-Cap Portfolio - Investment Class \| Financial Services Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	27.60%
Royce Capital Fund-Small-Cap Portfolio - Investment Class \| Energy Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	7.20%
Royce Capital Fund-Small-Cap Portfolio - Investment Class \| Cash and Cash Equivalents [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.80%
Royce Capital Fund-Small-Cap Portfolio - Investment Class \| Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.00%
Royce Capital Fund-Small-Cap Portfolio - Service Class \| TD SYNNEX [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.70%
Royce Capital Fund-Small-Cap Portfolio - Service Class \| M/I Homes [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.40%
Royce Capital Fund-Small-Cap Portfolio - Service Class \| Blue Bird [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.30%
Royce Capital Fund-Small-Cap Portfolio - Service Class \| Diebold Nixdorf [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.20%
Royce Capital Fund-Small-Cap Portfolio - Service Class \| Timberland Bancorp [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.00%
Royce Capital Fund-Small-Cap Portfolio - Service Class \| Village Super Market Cl. A [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.00%
Royce Capital Fund-Small-Cap Portfolio - Service Class \| IBEX [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.00%
Royce Capital Fund-Small-Cap Portfolio - Service Class \| Interface [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.00%
Royce Capital Fund-Small-Cap Portfolio - Service Class \| PulteGroup [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.00%
Royce Capital Fund-Small-Cap Portfolio - Service Class \| Unity Bancorp [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.80%
Royce Capital Fund-Small-Cap Portfolio - Service Class \| Industrial Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	16.90%
Royce Capital Fund-Small-Cap Portfolio - Service Class \| Information Technology Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	14.20%
Royce Capital Fund-Small-Cap Portfolio - Service Class \| Healthcare Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	8.70%
Royce Capital Fund-Small-Cap Portfolio - Service Class \| Consumer Discretionary Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	22.60%
Royce Capital Fund-Small-Cap Portfolio - Service Class \| Financial Services Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	27.60%
Royce Capital Fund-Small-Cap Portfolio - Service Class \| Energy Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	7.20%
Royce Capital Fund-Small-Cap Portfolio - Service Class \| Cash and Cash Equivalents [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.80%
Royce Capital Fund-Small-Cap Portfolio - Service Class \| Consumer Staples Sector [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.00%

Shareholder Report, Holdings (Details)

Jun. 30, 2026