Debt Obligations - Other Secured Notes Payable (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012
Debt Instrument [Line Items]
Balance	$ 136,016		$ 117,281
Max Facility Capacity	425,000		425,000
Total Other Secured Notes Payable	155,000		165,000
Revolving Inventory Facility [Member]
Debt Instrument [Line Items]
Balance	111,321		91,320
Max Facility Capacity	130,000		140,000	[1]
Stated Advance Rate	85.00%	[2]	85.00%	[2]
Interest Rate	3.75%	[3]	3.75%	[3]
Mortgage Note Payable [Member]
Debt Instrument [Line Items]
Balance	12,343		12,454
Interest Rate	5.87%	[3]	5.87%	[3]
Real Estate Credit Facility [Member]
Debt Instrument [Line Items]
Balance	10,806		11,733
Max Facility Capacity	25,000		25,000
Stated Advance Rate	70.00%		70.00%
Interest Rate	4.19%	[3]	4.21%	[3]
Equipment Note Payable [Member]
Debt Instrument [Line Items]
Balance	1,546		1,774
Interest Rate	4.25%	[3]	4.75%	[3]
LIBOR [Member] | Revolving Inventory Facility [Member]
Debt Instrument [Line Items]
Basis spread on variable interest rate	3.50%
LIBOR [Member] | Real Estate Credit Facility [Member]
Debt Instrument [Line Items]
Basis spread on variable interest rate	4.00%
Prime Rate [Member] | Equipment Note Payable [Member]
Debt Instrument [Line Items]
Basis spread on variable interest rate	1.00%
Seasonal Increase [Member] | Revolving Inventory Facility [Member]
Debt Instrument [Line Items]
Balance			$ 10,000

[1] Inclusive of a $10.0 million seasonal increase in the months of November through the end of January.

[2] Advance rate is based on qualifying vehicle cost and is secured by our entire vehicle inventory.

[3] Interest rate at period end equal to contractual benchmark plus index.