Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2019	Feb. 12, 2020	Jun. 28, 2019
Document Information [Line Items]
Entity Central Index Key	0001012019
Entity Registrant Name	RUSH ENTERPRISES INC \TX\
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2019
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	0-20797
Entity Incorporation, State or Country Code	TX
Entity Tax Identification Number	74-1733016
Entity Address, Address Line One	555 IH 35 South
Entity Address, City or Town	New Braunfels
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	78130
City Area Code	830
Local Phone Number	302-5200
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 1,193,177,826
Common Class B [Member]
Document Information [Line Items]
Title of 12(b) Security	Class B Common Stock, $0.01 par value
Trading Symbol	RUSHB
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		8,210,581
Common Class A [Member]
Document Information [Line Items]
Title of 12(b) Security	Class A Common Stock, $0.01 par value
Trading Symbol	RUSHA
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		28,042,484