Note 11 - Share Based Compensation and Employee Benefit Plans (Details Textual) - USD ($)				1 Months Ended	12 Months Ended
	Mar. 15, 2021	Jun. 16, 2020	Feb. 01, 2012	Oct. 31, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	May 12, 2020
Share-Based Payment Arrangement, Expense					$ 25,300,000	$ 22,200,000	$ 19,400,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross					511,900
Proceeds from Stock Options Exercised					$ 13,300,000	18,300,000	23,500,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period, Intrinsic Value					11,600,000	23,400,000	20,800,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested in Period, Fair Value					$ 5,900,000	$ 5,000,000.0	$ 4,500,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value					$ 16.81	$ 14.77	$ 6.36
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total					$ 10,600,000
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, Total					$ 19,400,000	$ 21,300,000
Cash Surrender Value of Life Insurance					13,000,000.0	12,700,000
Rush 401 Plan [Member]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	10.00%	10.00%	10.00%
Defined Contribution Plan, Cost					$ 12,100,000	$ 8,200,000	$ 6,000,000.0
Rush 401 Plan [Member] | Highly Compensated Employees [Member]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent					15.00%
Rush 401 Plan [Member] | Employees with Less than Five Years of Service [Member]
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	20.00%	5.00%	20.00%
Rush 401 Plan [Member] | Employees with More Than Five Years of Service [Member]
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	40.00%	10.00%	40.00%
Rush 401 Plan [Member] | Minimum [Member]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent					1.00%
Rush 401 Plan [Member] | Maximum [Member]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent					50.00%
Restricted Stock Units (RSUs) [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value					$ 13,800,000
Granted, weighted average grant date fair value (in dollars per share)					$ 50.00	$ 44.86	$ 21.98
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total					$ 10,900,000
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition						1 year 3 months 18 days
Common Class A [Member]
Share Price					$ 52.28
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
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant					460,602
Common Stock, Capital Shares Reserved for Future Issuance					2,700,000
Stock Issued During Period, Shares, Employee Stock Purchase Plans					134,115	148,999
Number of Employees Eligible to Participate in Stock Purchase Plan					7,418
Number of Employees Participating in Stock Purchase Plan					2,104
The 2006 Non-Employee Director Stock Option Plan [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized					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					134,643
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized					750,000
Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture, Total					13,509	15,726
The 2006 Non-Employee Director Stock Option Plan [Member] | Shares Issued to Three Non-employee Directors [Member] | Common Class A [Member]
Stock Issued During Period, Shares, New Issues					2,757	2,875
Issuance of Stock and Cash for Non-employee Director Compensation					$ 145,000
The 2006 Non-Employee Director Stock Option Plan [Member] | Shares Issued to Two Nonemployee Directors [Member] | Common Class A [Member]
Stock Issued During Period, Shares, New Issues					1,654	2,013
Payment to Nonemployee Directors					$ 58,000	$ 43,500
Issuance of Stock and Cash for Non-employee Director Compensation						$ 145,000
The 2006 Non-Employee Director Stock Option Plan [Member] | Shares Issued to One Nonemployee Director [Member] | Common Class A [Member]
Stock Issued During Period, Shares, New Issues					1,930	1,725
Payment to Nonemployee Directors					$ 43,500	$ 58,000
The 2006 Non-Employee Director Stock Option Plan [Member] | Shares Issued to One Director [Member] | Common Class A [Member]
Stock Issued During Period, Shares, New Issues				1,350
Share-Based Payment Arrangement, Expense				$ 72,500
Amended and Restated 2007 Incentive Plan [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Expiration Period					10 years
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period					3 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					1,756,629
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized					13,200,000			13,200,000
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					511,900	498,700
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					955,225
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized								4,800,000
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					354,600	340,650
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					4,800,000
Every 6 Months [Member] | Employee Stock Purchase Plan [Member]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount					$ 10,625