Credit Facilities (Details Textual) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($) loan	Dec. 31, 2017 USD ($)
Line of Credit Facility [Line Items]
Floorplan Offset	$ (74,359)	$ (86,547)
FMCC Offset	(24,000)	$ (22,500)
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity under line of credit facility	$ 1,800,000
Expiry date of Revolving Credit Facility	Jun. 17, 2021
Number of financial institutions | loan	24
Number of Manufacturer-affiliated finance companies | loan	6
Maximum Limit Of Restricted Payment Basket	the sum of $208.5 million plus (or minus if negative) (a) one-half of the aggregate consolidated net income for the period beginning on April 1, 2014 and ending on the date of determination and (b) the amount of net cash proceeds received from the sale of capital stock after June 2, 2014 and ending on the date of determination less (c) cash dividends and share repurchases after June 2, 2014
Restricted payment	$ 186,600
Brazil Credit Facilities [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Amount Outstanding	22,800
FMCC Facility [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity under line of credit facility	$ 300,000
Debt Instrument, Basis Spread on Variable Rate	1.50%
Line of Credit Facility, Fair Value of Amount Outstanding	$ 146,300
Available amount under borrowing capacity	$ 153,700
Debt interest rate	6.25%
Revolving Credit Facility, Floorplan Line [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Amount Outstanding	$ 1,087,000
Available amount under borrowing capacity	353,000
Floorplan Offset	$ (74,400)
Weighted average interest rate	0.00%	2.70%
Revolving Credit Facility, Floorplan Line, New Vehicles [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.25%
Revolving Credit Facility, Floorplan Line, Used Vehicles [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.50%
Revolving Credit Facility, Acquisition Line [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity under line of credit facility	$ 360,000
Line Of Credit Facility, Minimum Borrowing Capacity	$ 50,000
Debt Instrument, Basis Spread on Variable Rate	1.50%
Line of Credit Facility, Amount Outstanding	$ 28,035	$ 26,988
Available amount under borrowing capacity	307,500
Letters of credit outstanding	$ 25,000
Debt interest rate	2.30%
Rental Vehicle Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Amount Outstanding	$ 116,000
UK Credit Facilities [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Amount Outstanding	$ 149,600
Minimum [Member] | Brazil Credit Facilities [Member]
Line of Credit Facility [Line Items]
Debt interest rate	10.92%
Grace Period for Outstanding Borrowings	0 days
Minimum [Member] | UK Credit Facilities [Member]
Line of Credit Facility [Line Items]
Debt interest rate	1.25%
Maximum [Member] | Brazil Credit Facilities [Member]
Line of Credit Facility [Line Items]
Debt interest rate	16.77%
Grace Period for Outstanding Borrowings	90 days
Maximum [Member] | Rental Vehicle Credit Facility [Member]
Line of Credit Facility [Line Items]
Debt interest rate	6.25%
Maximum [Member] | UK Credit Facilities [Member]
Line of Credit Facility [Line Items]
Debt interest rate	3.95%
United States of America, Dollars | Maximum [Member] | Revolving Credit Facility, Acquisition Line [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.00%
Euros or Pound Sterling [Member] | Minimum [Member] | Revolving Credit Facility, Acquisition Line [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.25%
Euros or Pound Sterling [Member] | Maximum [Member] | Revolving Credit Facility, Acquisition Line [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.50%