Note 11 - Share Based Compensation and Employee Benefit Plans (Details Textual) - USD ($)	1 Months Ended	12 Months Ended			24 Months Ended
	Oct. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2023	May 16, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross		790,673
Share-Based Payment Arrangement, Expense		$ 30,400,000	$ 25,300,000	$ 22,200,000
Proceeds from Stock Options Exercised		18,000,000	13,300,000	18,300,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period, Intrinsic Value		19,800,000	11,600,000	23,400,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested in Period, Fair Value		$ 5,800,000	$ 5,900,000	$ 5,000,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value		$ 11.82	$ 11.21	$ 9.85
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount		$ 11,200,000			$ 11,200,000
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition		2 years 2 months 12 days
Deferred Compensation Plan [Member]
Deferred Compensation Arrangement with Individual, Vested Percentage		100.00%
Deferred Compensation Liability, Current		$ 24,800,000	$ 19,400,000		24,800,000
Cash Surrender Value of Life Insurance		18,000,000	13,000,000		$ 18,000,000
Rush 401 Plan [Member]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay					10.00%
Defined Contribution Plan, Cost		$ 13,300,000	12,100,000	$ 8,200,000
Rush 401 Plan [Member] | Maximum [Member]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent		1.00%			1.00%
Restricted Stock Units (RSUs) [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period		3 years
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value		$ 15,500,000
Granted, weighted average grant date fair value (in dollars per share)		$ 36.97		$ 29.91
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount			$ 12,200,000
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition			12 years 2 months 12 days
Highly Compensated Employees [Member] | Rush 401 Plan [Member]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent					15.00%
Employees with Less than Five Years of Service [Member] | Rush 401 Plan [Member]
Defined Contribution Plan, Employer Matching Contribution, Percent of Match		20.00%
Employees with More Than Five Years of Service [Member] | Rush 401 Plan [Member]
Defined Contribution Plan, Employer Matching Contribution, Percent of Match		40.00%
Common Class A [Member]
Share Price		$ 50.3			$ 50.3
Employee Stock Purchase Plan [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Purchase Price of Common Stock, Percent		85.00%
Maximum Fair Value for Employee Stock Purchase Per Year		$ 25,000			$ 25,000
Stock Issued During Period, Shares, Employee Stock Purchase Plans		208,854	201,173
Number of Employees Eligible to Participate in Stock Purchase Plan		7,860
Number of Employees Participating in Stock Purchase Plan		2,242
Employee Stock Purchase Plan [Member] | Common Class A [Member]
Employee Stock Ownership Plan (ESOP), Number of Allocated Shares						600,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant		1,082,000			1,082,000
Common Stock, Capital Shares Reserved for Future Issuance		4,650,000			4,650,000
The 2006 Non-Employee Director Stock Option Plan [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized		1,125,000			1,125,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Grant Date Aggregate Intrinsic Value		$ 750,000
Issuance of Cash for Non-employee Director Compensation, Percent		40.00%
The 2006 Non-Employee Director Stock Option Plan [Member] | Common Class A [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant		180,298			180,298
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized		1,125,000			1,125,000
Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture		21,667	20,264
The 2006 Non-Employee Director Stock Option Plan [Member] | Common Class A [Member] | Shares Issued to One Nonemployee Director [Member]
Stock Issued During Period, Shares, New Issues	1,501
Stock Issued During Period, Value, New Issues	$ 72,500
The 2006 Non-Employee Director Stock Option Plan [Member] | Common Class A [Member] | Shares Issued to Three Non-employee Directors [Member]
Stock Issued During Period, Shares, New Issues		4,116	2,757
Issuance of Stock and Cash for Non-employee Director Compensation		$ 145,000
The 2006 Non-Employee Director Stock Option Plan [Member] | Common Class A [Member] | Shares Issued to Two Nonemployee Directors [Member]
Stock Issued During Period, Shares, New Issues		2,469	1,654
Payment to Nonemployee Directors		$ 58,000	$ 58,000
The 2006 Non-Employee Director Stock Option Plan [Member] | Common Class A [Member] | Shares Issued to One Nonemployee Director [Member]
Stock Issued During Period, Shares, New Issues		2,880	1,930
Payment to Nonemployee Directors		$ 43,500	$ 43,500
Stock Issued During Period, Value, New Issues			$ 145,000
Amended and Restated 2007 Incentive Plan [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Expiration Period		10 years
Amended and Restated 2007 Incentive Plan [Member] | Common Class A [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant		3,684,518			3,684,518
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized						21,600,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Maximum Number of Shares Per Employee		150,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross		790,673	767,850
Amended and Restated 2007 Incentive Plan [Member] | Common Class B [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant		2,681,701			2,681,701
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized						9,000,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross		551,138	531,900
Amended and Restated 2007 Incentive Plan [Member] | Common Class B [Member] | Restricted Stock Units (RSUs) [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized		9,000,000			9,000,000
Every 6 Months [Member] | Employee Stock Purchase Plan [Member]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount		$ 10,625