Other Assets - Other Assets (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Other Assets [Line Items]
Other assets	$ 521,693	$ 410,305
Upfront fee
Other Assets [Line Items]
Other assets	136,250	140,000
Inventory of repossessed vehicles
Other Assets [Line Items]
Other assets	137,648	129,323
Manufacturer subvention payments receivable
Other Assets [Line Items]
Other assets	111,075	55,579
Derivative Assets
Other Assets [Line Items]
Other assets	46,666	29,875
Indemnification payments recoverable
Other Assets [Line Items]
Other assets	8,603	8,603
Other
Other Assets [Line Items]
Other assets	$ 81,451	$ 46,925