Condensed Financial Information of Custom Truck One Source, Inc. - Condensed Parent Company Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Condensed Financial Statements, Captions [Line Items]
Net cash flow (for) from operating activities	$ 310,112	$ 121,985	$ (30,883)
Net cash flow for investing activities	(282,463)	(187,485)	(176,598)
Repurchase of common stock	(32,575)	(28,984)	(38,845)
Net cash flows from financing activities	(25,268)	58,283	202,876
Net Change in Cash and Cash Equivalents	2,468	(6,504)	(4,051)
Cash and Cash Equivalents at Beginning of Period	3,805	10,309	14,360
Cash and Cash Equivalents at End of Period	6,273	3,805	10,309
Parent Company
Condensed Financial Statements, Captions [Line Items]
Net cash flow (for) from operating activities	(19,659)	(17,855)	68,723
Changes in investment in subsidiaries	53,414	48,187	(30,670)
Net cash flow for investing activities	53,414	48,187	(30,670)
Share-based payments	(1,180)	(1,728)	792
Repurchase of common stock	(32,575)	(28,604)	(38,845)
Net cash flows from financing activities	(33,755)	(30,332)	(38,053)
Net Change in Cash and Cash Equivalents	0	0	0
Cash and Cash Equivalents at Beginning of Period	0	0	0
Cash and Cash Equivalents at End of Period	$ 0	$ 0	$ 0