Credit Facilities (Details Textual) (USD $)			3 Months Ended				6 Months Ended		3 Months Ended						3 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013 Brazil Credit Facilities [Member] Maximum [Member]	Sep. 30, 2013 Brazil Credit Facilities [Member] Minimum [Member]	Sep. 30, 2013 FMCC Facility [Member]	Sep. 30, 2013 Revolving Credit Facility [Member] loan	Jun. 30, 2013 Revolving Credit Facility [Member]	Sep. 30, 2013 Revolving Credit Facility [Member] Acquisition Line [Member]	Sep. 30, 2013 Revolving Credit Facility [Member] Acquisition Line [Member] Maximum [Member]	Sep. 30, 2013 Revolving Credit Facility [Member] Acquisition Line [Member] Minimum [Member]	Sep. 30, 2013 Revolving Credit Facility [Member] Acquisition Line [Member] United States of America, Dollars Maximum [Member]	Sep. 30, 2013 Revolving Credit Facility [Member] Acquisition Line [Member] United States of America, Dollars Minimum [Member]	Sep. 30, 2013 Revolving Credit Facility [Member] Acquisition Line [Member] Euros or Pound Sterling [Member] Maximum [Member]	Sep. 30, 2013 Revolving Credit Facility [Member] Acquisition Line [Member] Euros or Pound Sterling [Member] Minimum [Member]	Sep. 30, 2013 Revolving Credit Facility [Member] Floorplan Line [Member]	Dec. 31, 2012 Revolving Credit Facility [Member] Floorplan Line [Member]	Sep. 30, 2013 Revolving Credit Facility [Member] Floorplan Line [Member] Maximum [Member]	Sep. 30, 2013 Revolving Credit Facility [Member] Floorplan Line [Member] Used Vehicle [Member]	Sep. 30, 2013 Revolving Credit Facility [Member] Floorplan Line [Member] New Vehicle [Member]	Sep. 30, 2013 Rental Vehicle Credit Facility [Member]	Sep. 30, 2013 UK Credit Facilities [Member] Maximum [Member]	Sep. 30, 2013 UK Credit Facilities [Member] Minimum [Member]
Credit Facility (Textual) [Abstract]
Debt Instrument, Basis Spread on Variable Rate					1.50%			1.50%			1.00%	0.00%	2.50%	1.50%				1.50%	1.25%
Maximum borrowing capacity under line of credit facility					$ 200,000,000	$ 1,700,000,000	$ 1,350,000,000		$ 320,000,000	$ 100,000,000			$ 125,000,000				$ 1,600,000,000
Number of financial institution						25
Number of Manufacturer-affiliated finance companies						6
Expiry date of Revolving Credit Facility						Jun. 20, 2018	Jun. 01, 2016
Line of credit facility, maximum borrowing capacity can be extended, amount						1,950,000,000
Commitment fees, Percentage									0.45%	0.25%					0.20%
Acquisition Line Minimum Commitment						100,000,000
Line of credit facility, unamortized cost						7,200,000
Line of Credit Facility, Amount Outstanding					153,100,000			0							908,200,000
Available amount under borrowing capacity					46,900,000			227,700,000							471,800,000
Immediately Available Funds	47,709,000	112,261,000													47,709,000
Weighted average interest rate															1.40%	1.70%
Maximum period for outstanding borrowing															1 year 0 months 0 days
Letters of credit outstanding								27,000,000
Restricted payment						$ 158,800,000
Maximum Limit of Restricted Payment						$125.0 million plus (or minus if negative) (a) one-half of the aggregate consolidated net income of the Company for the period beginning on January 1, 2013 and ending on the date of determination and (b) the amount of net cash proceeds received from the sale of capital stock on or after January 1, 2013 and ending on the date of determination less (c) cash dividends and share repurchases (“Restricted Payment Basket”)
Cancellation of agreement					0 years 0 months 30 days
Prime interest rate, minimum					3.50%
Debt interest rate			17.32%	13.28%	5.00%															5.00%	3.95%	1.16%
Debt Instrument Maturity Date Period			12 months	1 month