| Document and Entity Information | Aug. 03, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Aug. 3, 2021 |
| Entity Registrant Name | McGRATH RENTCORP |
| Entity Central Index Key | 0000752714 |
| Entity File Number | 000-13292 |
| Entity Incorporation State Country Code | CA |
| Entity Tax Identification Number | 94-2579843 |
| Entity Address, Address Line One | 5700 Las Positas Road |
| Entity Address, City or Town | Livermore |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 94551-7800 |
| City Area Code | 925 |
| Local Phone Number | 606-9200 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Security 12b Title | Common Stock |
| Trading Symbol | MGRC |
| Security Exchange Name | NASDAQ |
