Fair Value Of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes, Loans and Financing Receivable, Net	$ 10,598,353	$ 9,162,492
Restricted Cash and Investments	718,729	919,283
Restricted Cash and Cash Equivalents	118,492	136,556
Restricted Cash - Derivative Collateral	6,400	35,500
Interest Rate Swap Agreements - Assets	301	2,004
Interest Rate Cap Agreements Purchased	1,471	4,548
Securitized Debt Obligation Liability	9,005,203	6,937,841
Senior Notes	1,500,000	500,000
Convertible Senior Notes		500
Interest Rate Swap Agreements - Liabilities	301	6,440
Interest Rate Cap Agreements - Sold	1,501	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	1,805,981	572,297
Notes, Loans and Financing Receivable, Net	10,598,353	9,162,492
Restricted Cash and Investments	718,729	919,283
Restricted Cash and Cash Equivalents	118,492	136,556
Restricted Cash - Derivative Collateral	31,740	59,136
Interest Rate Swap Agreements - Assets	301	2,004
Interest Rate Cap Agreements Purchased	1,471	4,548
Syndicated And Lease Warehouse Facilities	374,496	802,571
Medium Term Note Faciltiy and Wachovia Funding Facility	182,450	296,820
Securitization Notes Payable - Public Transactions	8,449,985	6,937,841
Securitization Notes Payable - Private Transactions	555,218
Senior Notes	1,500,000	500,000
Convertible Senior Notes		500
Interest Rate Swap Agreements - Liabilities	301	6,440
Interest Rate Cap Agreements - Sold	1,501	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	1,805,981	572,297
Notes, Loans and Financing Receivable, Net	10,956,980	9,385,851
Restricted Cash and Investments	718,729	919,283
Restricted Cash and Cash Equivalents	118,492	136,556
Restricted Cash - Derivative Collateral	31,740	59,136
Interest Rate Swap Agreements - Assets	301	2,004
Interest Rate Cap Agreements Purchased	1,471	4,548
Syndicated And Lease Warehouse Facilities		802,571
Medium Term Note Faciltiy and Wachovia Funding Facility	182,689	296,542
Securitization Notes Payable - Public Transactions	8,584,572	6,945,865
Securitization Notes Payable - Private Transactions	567,935
Senior Notes	1,580,000	510,000
Convertible Senior Notes		500
Interest Rate Swap Agreements - Liabilities	301	6,440
Interest Rate Cap Agreements - Sold	1,501	4,768
Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest Rate Cap Agreements Purchased	1,471	4,548
Interest Rate Cap Agreements - Sold	1,501	4,768
Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest Rate Swap Agreements - Assets	301	2,004
Interest Rate Swap Agreements - Liabilities	$ 301	$ 6,440