Note 11 - Share Based Compensation and Employee Benefit Plans (Details Textual) - USD ($)	1 Months Ended	12 Months Ended
	Oct. 31, 2024	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	May 16, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross		538,700
Share-Based Payment Arrangement, Expense		$ 30,400,000	$ 30,400,000	$ 25,300,000
Proceeds from Stock Options Exercised		25,400,000	18,000,000	13,300,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period, Intrinsic Value		47,300,000	19,800,000	11,600,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested in Period, Fair Value		$ 5,800,000	$ 5,800,000	$ 5,900,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value		$ 17.13	$ 11.82	$ 11.21
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount		$ 12,400,000
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition		2 years 1 month 6 days
Deferred Compensation Plan [Member]
Deferred Compensation Arrangement with Individual, Vested Percentage		100.00%
Deferred Compensation Liability, Current		$ 28,100,000	$ 24,800,000
Cash Surrender Value of Life Insurance		$ 24,400,000	18,000,000
Rush 401 Plan [Member]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay		10.00%
Defined Contribution Plan, Cost		$ 14,000,000	$ 13,300,000	$ 12,100,000
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, Award Vesting Period		3 years
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value		$ 9,200,000
Granted, weighted average grant date fair value (in dollars per share)		$ 50.64	$ 36.97	$ 33.33
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount		$ 13,500,000
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition		1 year 3 months 18 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		$ 54.79
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
Stock Issued During Period, Shares, Employee Stock Purchase Plans		195,540	208,854
Number of Employees Eligible to Participate in Stock Purchase Plan		7,391
Number of Employees Participating in Stock Purchase Plan		2,262
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		886,509
Common Stock, Capital Shares Reserved for Future Issuance		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
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Grant Date Aggregate Intrinsic Value		$ 145,000
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		162,533
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized		1,125,000
Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture		17,765	21,667
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		3,230	4,116
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		1,938	2,469
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		2,261	2,880
Payment to Nonemployee Directors		$ 43,499	$ 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		3,189,695
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized		21,600,000			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		538,700	790,673
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		2,283,175
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, Maximum Number of Shares Per Employee		150,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross		398,525	551,138
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
Every 6 Months [Member] | Employee Stock Purchase Plan [Member]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount		$ 10,625