Note 2 - Significant Accounting Policies (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Feb. 25, 2019
Depreciation, Total	$ 148,300	$ 157,800	$ 158,700
Amortization, Total	21,200	19,500	16,800
Goodwill, Impairment Loss	0
Capitalized Computer Software, Net, Ending Balance	5,500	7,000
Capitalized Computer Software, Amortization	1,500	1,900
Indefinite-Lived Franchise Rights	8,600	7,000
Advertising Expense	7,500	7,900	$ 11,500
Capitalized Computer Software, Accumulated Amortization	13,600	12,100
Other Noncurrent Liabilities [Member] | Financial Guarantee [Member]
Guarantor Obligations, Current Carrying Value	5,200	5,200
Equity Method Investments	36,700
Rush Truck Centres of Canada Limited [Member]
Equity Method Investment, Ownership Percentage			50.00%	50.00%
Rush Truck Centres of Canada Limited [Member] | Call Option [Member]
Equity Method Investment, Remaining Ownership Percentage Not Yet Acquired				50.00%
Rush Truck Centres of Canada Limited [Member] | Call Option [Member] | Other Assets [Member]
Call Option, Fair Value Disclosure	3,600
Computer Software, Intangible Asset [Member]
Finite-Lived Intangible Asset, Expected Amortization, Year One	1,200
Finite-Lived Intangible Asset, Expected Amortization, Year Two	1,200
Finite-Lived Intangible Asset, Expected Amortization, Year Three	1,200
Finite-Lived Intangible Asset, Expected Amortization, Year Four	1,200
Franchise Rights [Member]
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)	0
Vehicles [Member]
Depreciation, Total	116,100	$ 119,900	$ 120,100
Finance Lease, Right-of-Use Asset, after Accumulated Amortization, Total	108,500
Finance Lease, Right-of-Use Asset, Accumulated Amortization	$ 43,500