Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Oct. 27, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Trading Symbol	MGRC
Security Exchange Name	NASDAQ
Entity Registrant Name	McGRATH RENTCORP
Entity Central Index Key	0000752714
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Title of 12(b) Security	Common Stock
Entity File Number	000-13292
Entity Incorporation, State or 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
Entity Common Stock, Shares Outstanding		24,246,568
Document Quarterly Report	true
Document Transition Report	false