Debt - Summary of Secured Structured Financings (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended		12 Months Ended
	Jun. 30, 2014		Dec. 31, 2013
Debt Instrument [Line Items]
Balance	$ 18,391,660	[1]	$ 15,195,887
Notes payable — credit facilities, $3,300,000 and $3,650,000 to affiliates, respectively	7,762,950	[2]	8,099,773
Restricted Cash	103,287		89,118
Secured Structured Financings
Debt Instrument [Line Items]
Balance	18,391,660		15,195,887
Notes payable — credit facilities, $3,300,000 and $3,650,000 to affiliates, respectively	37,995,544		33,127,485
Collateral	23,487,790		19,133,315
Restricted Cash	1,509,767		1,280,881
Secured Structured Financings | 2010 Securitizations
Debt Instrument [Line Items]
Balance	333,148		632,251
Notes payable — credit facilities, $3,300,000 and $3,650,000 to affiliates, respectively	3,671,749		4,671,749
Collateral	641,669		1,143,435
Restricted Cash	142,992		205,190
Secured Structured Financings | 2010 Securitizations | Minimum
Debt Instrument [Line Items]
Original Estimated Maturity Dates	2016-10		2016-10
Initial Weighted Average Interest Rate	1.04%		1.04%
Secured Structured Financings | 2010 Securitizations | Maximum
Debt Instrument [Line Items]
Original Estimated Maturity Dates	2017-11		2017-11
Initial Weighted Average Interest Rate	1.44%		1.44%
Secured Structured Financings | 2011 Securitizations
Debt Instrument [Line Items]
Balance	653,968		1,218,208
Notes payable — credit facilities, $3,300,000 and $3,650,000 to affiliates, respectively	4,693,289		5,605,609
Collateral	1,038,660		1,634,220
Restricted Cash	157,307		195,854
Secured Structured Financings | 2011 Securitizations | Minimum
Debt Instrument [Line Items]
Original Estimated Maturity Dates	2015-10		2015-10
Initial Weighted Average Interest Rate	1.21%		1.21%
Secured Structured Financings | 2011 Securitizations | Maximum
Debt Instrument [Line Items]
Original Estimated Maturity Dates	2017-09		2017-09
Initial Weighted Average Interest Rate	2.80%		2.80%
Secured Structured Financings | 2012 Securitizations
Debt Instrument [Line Items]
Balance	3,088,855		4,061,127
Notes payable — credit facilities, $3,300,000 and $3,650,000 to affiliates, respectively	8,023,840		8,023,840
Collateral	3,899,764		5,013,135
Restricted Cash	355,658		383,677
Secured Structured Financings | 2012 Securitizations | Minimum
Debt Instrument [Line Items]
Original Estimated Maturity Dates	2017-11		2017-11
Initial Weighted Average Interest Rate	0.92%		0.92%
Secured Structured Financings | 2012 Securitizations | Maximum
Debt Instrument [Line Items]
Original Estimated Maturity Dates	2018-12		2018-12
Initial Weighted Average Interest Rate	1.68%		1.68%
Secured Structured Financings | 2013 Securitizations
Debt Instrument [Line Items]
Balance	4,338,610		5,503,580
Notes payable — credit facilities, $3,300,000 and $3,650,000 to affiliates, respectively	6,689,700		6,689,700
Collateral	5,295,330		6,465,840
Restricted Cash	348,040		351,160
Secured Structured Financings | 2013 Securitizations | Minimum
Debt Instrument [Line Items]
Original Estimated Maturity Dates	2019-01		2019-01
Initial Weighted Average Interest Rate	0.89%		0.89%
Secured Structured Financings | 2013 Securitizations | Maximum
Debt Instrument [Line Items]
Original Estimated Maturity Dates	2021-01		2021-01
Initial Weighted Average Interest Rate	1.59%		1.59%
Secured Structured Financings | 2014 Securitizations
Debt Instrument [Line Items]
Balance	3,706,441
Notes payable — credit facilities, $3,300,000 and $3,650,000 to affiliates, respectively	4,100,000
Collateral	4,385,840
Restricted Cash	236,269
Secured Structured Financings | 2014 Securitizations | Minimum
Debt Instrument [Line Items]
Original Estimated Maturity Dates	2020-04
Initial Weighted Average Interest Rate	1.63%
Secured Structured Financings | 2014 Securitizations | Maximum
Debt Instrument [Line Items]
Original Estimated Maturity Dates	2020-08
Initial Weighted Average Interest Rate	1.72%
Secured Structured Financings | Public Securitizations
Debt Instrument [Line Items]
Balance	12,121,022		11,415,166
Notes payable — credit facilities, $3,300,000 and $3,650,000 to affiliates, respectively	27,178,578		24,990,898
Collateral	15,261,263		14,256,630
Restricted Cash	1,240,266		1,135,881
Secured Structured Financings | 2010 Private Issuance
Debt Instrument [Line Items]
Balance	209,128		219,704
Notes payable — credit facilities, $3,300,000 and $3,650,000 to affiliates, respectively	516,000		516,000
Initial Weighted Average Interest Rate	1.29%		1.29%
Collateral	338,513		378,434
Restricted Cash	9,538		8,435
Secured Structured Financings | 2010 Private Issuance | Maximum
Debt Instrument [Line Items]
Original Estimated Maturity Dates	2011-06		2011-06
Secured Structured Financings | 2011 Private Issuances
Debt Instrument [Line Items]
Balance	1,222,065		662,138
Notes payable — credit facilities, $3,300,000 and $3,650,000 to affiliates, respectively	4,856,525		4,856,525
Collateral	1,652,724		908,304
Restricted Cash	56,942		36,449
Secured Structured Financings | 2011 Private Issuances | Minimum
Debt Instrument [Line Items]
Initial Weighted Average Interest Rate	1.46%		1.46%
Secured Structured Financings | 2011 Private Issuances | Maximum
Debt Instrument [Line Items]
Original Estimated Maturity Dates	2018-12		2018-12
Initial Weighted Average Interest Rate	1.80%		1.80%
Secured Structured Financings | 2012 Private Issuance
Debt Instrument [Line Items]
Balance	14,962		30,526
Notes payable — credit facilities, $3,300,000 and $3,650,000 to affiliates, respectively	70,308		70,308
Initial Weighted Average Interest Rate	1.07%		1.07%
Collateral	20,177		35,378
Restricted Cash	1,874		3,016
Secured Structured Financings | 2012 Private Issuance | Maximum
Debt Instrument [Line Items]
Original Estimated Maturity Dates	2016-05		2016-05
Secured Structured Financings | 2013 Private Issuance
Debt Instrument [Line Items]
Balance	2,411,661		2,868,353
Notes payable — credit facilities, $3,300,000 and $3,650,000 to affiliates, respectively	2,693,754		2,693,754
Collateral	3,249,917		3,554,569
Restricted Cash	89,031		97,100
Secured Structured Financings | 2013 Private Issuance | Minimum
Debt Instrument [Line Items]
Original Estimated Maturity Dates	2018-09		2018-09
Initial Weighted Average Interest Rate	1.13%		1.13%
Secured Structured Financings | 2013 Private Issuance | Maximum
Debt Instrument [Line Items]
Original Estimated Maturity Dates	2020-09		2020-09
Initial Weighted Average Interest Rate	1.38%		1.38%
Secured Structured Financings | 2014 Private Issuance
Debt Instrument [Line Items]
Balance	2,412,822
Notes payable — credit facilities, $3,300,000 and $3,650,000 to affiliates, respectively	2,680,379
Collateral	2,965,196
Restricted Cash	112,116
Secured Structured Financings | 2014 Private Issuance | Minimum
Debt Instrument [Line Items]
Original Estimated Maturity Dates	2018-03
Initial Weighted Average Interest Rate	1.09%
Secured Structured Financings | 2014 Private Issuance | Maximum
Debt Instrument [Line Items]
Original Estimated Maturity Dates	2021-08
Initial Weighted Average Interest Rate	1.85%
Secured Structured Financings | Privately Issued Amortizing Notes
Debt Instrument [Line Items]
Balance	6,270,638		3,780,721
Notes payable — credit facilities, $3,300,000 and $3,650,000 to affiliates, respectively	10,816,966		8,136,587
Collateral	8,226,527		4,876,685
Restricted Cash	$ 269,501		$ 145,000

[1] Notes payable — secured structured financings — The estimated fair value of notes payable related to secured structured financings is calculated based on market quotes for the Company’s publicly traded debt and estimated market rates currently available from recent transactions involving similar debt with similar credit risks, and is considered a Level 2 measurement.

[2] Notes payable — credit facilities — The carrying amount of notes payable related to revolving credit facilities is estimated to approximate fair value as of June 30, 2014 and December 31, 2013. Management believes that the terms of these credit agreements approximate market terms for similar credit agreements. The fair value of notes payable is considered a Level 3 measurement.