| Cover Page | Nov. 09, 2021 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Nov. 9, 2021 |
| Entity Registrant Name | CUSTOM TRUCK ONE SOURCE, INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-38186 |
| Entity Tax Identification Number | 84-2531628 |
| Entity Address, Address Line One | 7701 Independence Avenue |
| Entity Address, City or Town | Kansas City |
| Entity Address, State or Province | MO |
| Entity Address, Postal Zip Code | 64125 |
| City Area Code | 816 |
| Local Phone Number | 241-4888 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Amendment Flag | false |
| Entity Central Index Key | 0001709682 |
| Common Stock | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Common Stock, $0.0001 par value |
| Trading Symbol | CTOS |
| Security Exchange Name | NYSE |
| Redeemable Warrants | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Redeemable warrants, exercisable for Common Stock, $0.0001 par value |
| Trading Symbol | CTOS.WS |
| Security Exchange Name | NYSE |
