Fair Value Of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financing Receivable, Net	$ 10,998,274	$ 9,162,492
Restricted Cash and Investments	728,908	919,283
Restricted Cash and Cash Equivalents	14,808	136,556
Restricted Cash - Derivative Collateral	4,200	35,500
Interest Rate Swap Agreements - Assets	133	2,004
Interest Rate Cap Agreements Purchased	386	4,548
Securitized Debt Obligation Liability	9,023,308	6,937,841
Senior Notes	1,500,000	500,000
Convertible Senior Notes		500
Interest Rate Swap Agreements - Liabilities	133	6,440
Interest Rate Cap Agreements - Sold	394	4,768
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	1,289,494	572,297
Financing Receivable, Net	10,998,274	9,162,492
Restricted Cash and Investments	728,908	919,283
Restricted Cash and Cash Equivalents	14,808	136,556
Restricted Cash - Derivative Collateral	24,774	59,136
Interest Rate Swap Agreements - Assets	133	2,004
Interest Rate Cap Agreements Purchased	386	4,548
Syndicated And Lease Warehouse Facilities	354,203	802,571
Medium Term Note Faciltiy and Wachovia Funding Facility		296,820
Securitization Notes Payable - Public Transactions	8,533,321	6,937,841
Securitization Notes Payable - Private Transactions	489,987
Senior Notes	1,500,000	500,000
Convertible Senior Notes		500
Interest Rate Swap Agreements - Liabilities	133	6,440
Interest Rate Cap Agreements - Sold	394	4,768
Portion at Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	1,289,494	572,297
Financing Receivable, Net	11,313,481	9,385,851
Restricted Cash and Investments	728,908	919,283
Restricted Cash and Cash Equivalents	14,808	136,556
Restricted Cash - Derivative Collateral	24,774	59,136
Interest Rate Swap Agreements - Assets	133	2,004
Interest Rate Cap Agreements Purchased	386	4,548
Syndicated And Lease Warehouse Facilities		802,571
Medium Term Note Faciltiy and Wachovia Funding Facility		296,542
Securitization Notes Payable - Public Transactions	8,669,106	6,945,865
Securitization Notes Payable - Private Transactions	502,332
Senior Notes	1,620,000	510,000
Convertible Senior Notes		500
Interest Rate Swap Agreements - Liabilities	133	6,440
Interest Rate Cap Agreements - Sold	394	4,768
Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest Rate Cap Agreements Purchased	386	4,548
Interest Rate Cap Agreements - Sold	394	4,768
Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest Rate Swap Agreements - Assets	133	2,004
Interest Rate Swap Agreements - Liabilities	$ 133	$ 6,440