Summary of Significant Accounting Policies and Estimates Summary of Significant Account Policies and Estimates (Details Textuals)	3 Months Ended						12 Months Ended
	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015	Mar. 31, 2014	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Summary of Significant Accounting Policies and Estimates [Line Items]
Reclassified debt issuance costs, current	$ 500,000						$ 500,000
Value of used vehicle inventory financed							85.00%
Number of Reportable Segments							3
Change in the historical chargeback results used in determining estimates of future amounts	10.00%						10.00%
Change in the reserve of future amounts	$ 3,800,000						$ 3,800,000
Restricted cash and short term investments	85,100,000			$ 136,300,000			85,100,000	$ 136,300,000
Inventory cost reduced for interest assistance received from manufacturers	9,600,000			10,300,000			9,600,000	10,300,000
Reduction in new vehicle cost of sales	$ 49,200,000			50,500,000			$ 49,200,000	50,500,000	$ 45,100,000
Number of geographic regions							4
Weighted Income approach to determine the fair value of the Company's reporting units	80.00%						80.00%
Weighted Market approach to determine the fair value of the Company's reporting units	20.00%						20.00%
Recovery back to normalized levels by 2016	17,300,000						17,300,000
Advertising expenses							$ 75,300,000	74,600,000	73,800,000
Reduction in advertising expenses							$ 16,700,000	17,300,000	16,600,000
Percentage of Company's new vehicle sales volume more than which no other manufacturer accounted for							2.70%
Accounts Receivable, Gross, Current	$ 176,260,000			160,972,000			$ 176,260,000	160,972,000
Interest paid							109,300,000	92,000,000	80,200,000
Income taxes refundable							$ 56,900,000	74,800,000	62,300,000
Percentage of change in loss reserve due to change in actuarial loss rate per employee	10.00%						10.00%
Change in loss reserve due to change in actuarial loss rate per employee	$ 2,100,000						$ 2,100,000
Maximum payout under first layer							0
Limited exposure in no stop loss plan per occurrence							1,000,000
Amount Accrued for Stop Loss Plans	400,000						400,000
Amount Accrued for No Stop Loss Plans	20,400,000						20,400,000
Maximum potential loss exposure under all of the Stop Loss Plans before consideration of amounts previously paid or accruals recorded	34,900,000						34,900,000
Remaining potential loss exposure in Stop Loss Plan	13,600,000						13,600,000
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)	19,200,000	$ 10,600,000	$ 200,000	85,500,000			30,000,000	30,100,000	$ 31,000,000
Reclassified debt issuance costs, long-term	3,600,000						3,600,000
Reclassified current deferred tax assets	$ 14,100,000						$ 14,100,000
Used vehicle days supply							35 days
FCA US [Member]
Summary of Significant Accounting Policies and Estimates [Line Items]
Share in company sales volume							4.00%
Share in company receivable balance	3.00%						3.00%
Toyota [Member]
Summary of Significant Accounting Policies and Estimates [Line Items]
Share in company sales volume							24.90%
Share in company receivable balance	17.00%						17.00%
BMW [Member]
Summary of Significant Accounting Policies and Estimates [Line Items]
Share in company sales volume							13.50%
Share in company receivable balance	13.00%						13.00%
Ford [Member]
Summary of Significant Accounting Policies and Estimates [Line Items]
Share in company sales volume							11.00%
Share in company receivable balance	9.00%						9.00%
Daimler [Member]
Summary of Significant Accounting Policies and Estimates [Line Items]
Share in company sales volume							4.30%
Share in company receivable balance	14.00%						14.00%
General Motors [Member]
Summary of Significant Accounting Policies and Estimates [Line Items]
Share in company sales volume							7.40%
Share in company receivable balance	15.00%						15.00%
Nissan [Member]
Summary of Significant Accounting Policies and Estimates [Line Items]
Share in company sales volume							7.10%
Share in company receivable balance	6.00%						6.00%
Honda [Member]
Summary of Significant Accounting Policies and Estimates [Line Items]
Share in company sales volume							9.90%
Share in company receivable balance	2.00%						2.00%
Hyundai [Member]
Summary of Significant Accounting Policies and Estimates [Line Items]
Share in company sales volume							4.20%
Share in company receivable balance	3.00%						3.00%
Volkswagen [Member]
Summary of Significant Accounting Policies and Estimates [Line Items]
Share in company sales volume							11.00%
Share in company receivable balance	12.00%						12.00%
5.00% Senior Note [Member]
Summary of Significant Accounting Policies and Estimates [Line Items]
Unsecured Long-term Debt, Noncurrent	$ 540,465,000			538,933,000			$ 540,465,000	538,933,000
Long-term Debt, Fair Value	548,400,000			545,900,000			548,400,000	545,900,000
5.25% Senior Note [Member]
Summary of Significant Accounting Policies and Estimates [Line Items]
Unsecured Long-term Debt, Noncurrent	295,591,000			295,156,000			295,591,000	295,156,000
Long-term Debt, Fair Value	297,000,000			297,800,000			297,000,000	297,800,000
Real Estate Related and Other Long Term Debt [Member]
Summary of Significant Accounting Policies and Estimates [Line Items]
Other Long-term Debt	$ 385,358,000			$ 365,564,000			385,358,000	$ 365,564,000
Maximum [Member]
Summary of Significant Accounting Policies and Estimates [Line Items]
Interest assistance received related to vehicles sold					139.90%
Per Occurrence Company Deductible							10,000,000
Aggregate deductible							$ 30,000,000
Minimum [Member]
Summary of Significant Accounting Policies and Estimates [Line Items]
Interest assistance received related to vehicles sold						90.00%
U.S.
Summary of Significant Accounting Policies and Estimates [Line Items]
Company operates in different states	14						14