Document And Entity Information (USD $)	12 Months Ended
	Dec. 31, 2012	Jun. 29, 2012	Mar. 01, 2013 Common Class A [Member]	Mar. 01, 2013 Common Class B [Member]
Entity Registrant Name	RUSH ENTERPRISES INC \TX\
Document Type	10-K
Current Fiscal Year End Date	--12-31
Entity Common Stock, Shares Outstanding			28,387,201	10,792,223
Entity Public Float		$ 541,429,901
Amendment Flag	false
Entity Central Index Key	0001012019
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Well-known Seasoned Issuer	No
Document Period End Date	Dec. 31, 2012
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	FY