Related-Party Transactions - Additional Information (Details) (USD $)	3 Months Ended		6 Months Ended			3 Months Ended	6 Months Ended	12 Months Ended	3 Months Ended	6 Months Ended	0 Months Ended	3 Months Ended	6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended	6 Months Ended	3 Months Ended		6 Months Ended		3 Months Ended	6 Months Ended			3 Months Ended	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Jun. 30, 2014 Dealer Loan Portfolio	Jun. 30, 2014 Dealer Loan Portfolio	Dec. 31, 2013 Dealer Loan Portfolio	Jun. 30, 2014 SHUSA	Jun. 30, 2014 SHUSA	Jun. 27, 2014 SBNA	Jun. 30, 2014 SBNA	Jun. 30, 2014 SBNA	Jun. 27, 2014 SBNA	Jun. 30, 2014 SBNA Serviced Auto Loan and Retail Installment	Jun. 30, 2013 SBNA Serviced Auto Loan and Retail Installment	Jun. 30, 2014 SBNA Serviced Auto Loan and Retail Installment	Jun. 30, 2013 SBNA Serviced Auto Loan and Retail Installment	Jun. 30, 2014 Produban Servicios Informaticos Generales S.L	Jun. 30, 2013 Produban Servicios Informaticos Generales S.L	Jun. 30, 2014 Produban Servicios Informaticos Generales S.L	Jun. 30, 2013 Produban Servicios Informaticos Generales S.L	Jun. 30, 2014 Cost Method Investment	Jun. 30, 2014 Cost Method Investment	Jun. 30, 2014 Former Managing Member	Jun. 30, 2013 Former Managing Member	Jun. 30, 2014 Former Managing Member	Jun. 30, 2013 Former Managing Member	Jun. 30, 2014 Chairman and CEO Expenses Paid for Use of CEO Private Plane	Jun. 30, 2014 Chairman and CEO Expenses Paid for Use of CEO Private Plane	Jun. 30, 2014 Chairman and CEO, President and CFO and Board Member	Oct. 21, 2013 Chairman and CEO, President and CFO and Board Member sqft	Jun. 30, 2014 Chairman and CEO, President and CFO and Board Member Rent Expense	Jun. 30, 2014 Chairman and CEO, President and CFO and Board Member Rent Expense
Class of Stock [Line Items]
Interest expense on line of credit	$ 22,709,000	$ 13,957,000	$ 47,583,000	$ 20,451,000					$ 1,299,000	$ 1,662,000
Accrued interest expense on line of credit	6,146,000		6,146,000		11,435,000				213,000	213,000
Letter of credit fees	126,000	144,000	251,000	270,000
Accrued fees on letter of credit	126,000		126,000		128,000
Notional	14,619,274,000		14,619,274,000		10,461,378,000
Derivative instrument interest expenses	12,702,000	1,289,000	21,583,000	6,163,000
Receivables sold								222,384,000
Servicing fee income on receivables sold						3,033,000	4,298,000								5,784,000	3,157,000	6,649,000	9,371,000
Servicing fees receivables						1,259,000	1,723,000					6,937,000	10,622,000
Leased vehicles, net	3,567,546,000		3,567,546,000		2,023,433,000									369,114,000
Leased vehicles, net														317,275,000
Proceeds from sale											322,851,000
Total gain from sale											5,576,000
Servicing fee income	22,099,000	6,355,000	32,504,000	13,626,000								535,000	629,000
Credit loss indemnification of leases												48,226,000	48,226,000
Expenses incurred																			22,000	22,000	75,000	75,000
Origination in unsecured revolving loans			87,217,000	283,406,000																			2,207,000	2,911,000
Reimbursed expenses																									0	97,000	0	478,000
Related party, amount of transaction																													141,000	414,000			54,000	108,000
Average hourly rate (in usd per hour)			5,800
Area of leased property (in square foot)																																373,000
Lease term																															12 years
Future minimum payment of lease																															$ 83,555,000