Secured Debt Agreements - Additional Information (Detail)				3 Months Ended			12 Months Ended
	Apr. 22, 2016 USD ($) ExtensionOptions	Apr. 04, 2016 USD ($) ExtensionOptions	Mar. 31, 2016 USD ($) ExtensionOptions	Mar. 31, 2016 USD ($) ExtensionOptions Assets	Dec. 31, 2015 USD ($)	Jun. 30, 2015 USD ($) ExtensionOptions	Dec. 31, 2015 USD ($)
Debt Instrument [Line Items]
Maturity date				Aug. 31, 2016
Secured debt agreements borrowings outstanding			$ 6,311,659,000	$ 6,311,659,000	$ 6,116,105,000		$ 6,116,105,000
Covenants, minimum tangible net worth			$ 1,900,000,000	$ 1,900,000,000
Covenants, percentage of tangible assets on cash proceeds from equity issuances				75.00%
Covenants, percentage of recourse indebtedness			5.00%	5.00%
Minimum [Member]
Debt Instrument [Line Items]
Covenants, EBITDA to fixed charges, in percent				140.00%
Covenants, minimum cash liquidity amount			$ 10,000,000	$ 10,000,000
Maximum [Member]
Debt Instrument [Line Items]
Covenants, indebtedness to total assets, in percent			83.33%	83.33%
Asset-Specific Financings [Member]
Debt Instrument [Line Items]
Weighted-average outstanding balance				$ 141,400,000	224,800,000
Closing of asset specific financings | Assets				2
Additional credit capacity				$ 232,400,000
Revolving Repurchase Facilities [Member]
Debt Instrument [Line Items]
Weighted-average outstanding balance				3,100,000,000	2,800,000,000
Aggregate borrowings			$ 3,300,000,000	$ 3,300,000,000	2,900,000,000		$ 2,900,000,000
Weighted-average advance rate				79.20%			79.10%
Weighted-average initial maturity				1 year 3 months 18 days			1 year 4 months 24 days
Approximate credit line amount			4,730,915,000	$ 4,730,915,000	4,804,267,000		$ 4,804,267,000
Amount available for potential future fundings of loan			464,324,000	464,324,000	504,778,000		504,778,000
Current borrowing capacity			3,716,729,000	$ 3,716,729,000	3,363,492,000		3,363,492,000
Revolving Repurchase Facilities [Member] | Wells Fargo [Member]
Debt Instrument [Line Items]
Weighted-average advance rate				79.50%
Approximate credit line amount			1,172,000,000	$ 1,172,000,000	1,172,000,000		1,172,000,000
Amount available for potential future fundings of loan			133,558,000	$ 133,558,000	132,077,000		132,077,000
Borrowings maturity term				Term matched
Current borrowing capacity			1,005,043,000	$ 1,005,043,000	817,562,000		817,562,000
Revolving Repurchase Facilities [Member] | Bank of America [Member]
Debt Instrument [Line Items]
Weighted-average advance rate				79.50%
Approximate credit line amount			$ 750,000,000	$ 750,000,000	750,000,000		750,000,000
Number of extension options | ExtensionOptions			2	2
Term of maturity date				1 year
Amount available for potential future fundings of loan			$ 47,331,000	$ 47,331,000	46,917,000		46,917,000
Borrowings maturity term				May 21, 2021
Current borrowing capacity			666,275,000	$ 666,275,000	665,861,000		665,861,000
Maturity period				Includes two one-year extension options which may be exercised at our sole discretion.
Revolving Repurchase Facilities [Member] | MetLife [Member]
Debt Instrument [Line Items]
Weighted-average advance rate				78.50%
Approximate credit line amount			$ 695,945,000	$ 695,945,000	750,000,000		750,000,000
Number of extension options | ExtensionOptions			5	5
Term of maturity date				1 year
Amount available for potential future fundings of loan			$ 128,262,000	$ 128,262,000	138,262,000		138,262,000
Borrowings maturity term				February 24, 2021
Current borrowing capacity			594,369,000	$ 594,369,000	462,849,000		462,849,000
Maturity period				Includes five one-year extension options which may be exercised at our sole discretion.
Revolving Repurchase Facilities [Member] | MetLife [Member] | Subsequent Events [Member]
Debt Instrument [Line Items]
Approximate credit line amount	$ 1,000,000,000
Maturity date	Apr. 22, 2022
Number of extension options | ExtensionOptions	5
Term of maturity date	1 year
Additional credit capacity	$ 304,100,000
Maturity period	Inclusive of five one-year extension options, exercisable at our option
Revolving Repurchase Facilities [Member] | Extended Maturity [Member] | Bank of America [Member]
Debt Instrument [Line Items]
Approximate credit line amount			$ 750,000,000	$ 750,000,000
Maturity date				May 21, 2021
Number of extension options | ExtensionOptions			2	2
Term of maturity date				1 year
GE Portfolio Acquisition Facility [Member] | Sequential Repay Advance [Member]
Debt Instrument [Line Items]
Term of maturity date						1 year
Secured debt agreements borrowings outstanding					40,700,000		40,700,000
Current borrowing capacity						$ 237,200,000
Percentage of additional advance						5.00%
Sequential Repay Advance, percentage of guarantee rate						100.00%
GE Portfolio Acquisition Facility [Member] | Wells Fargo [Member]
Debt Instrument [Line Items]
Approximate credit line amount			$ 3,100,000,000	$ 3,100,000,000
Approximate credit line, outstanding amount			2,900,000,000
Amount available for potential future fundings of loan			133,900,000	$ 133,900,000
GE Portfolio Acquisition Facility [Member] | Asset Specific Borrowings [Member]
Debt Instrument [Line Items]
Maturity date				May 20, 2020
Number of extension options | ExtensionOptions						2
Term of maturity date						1 year
Weighted average rate						80.00%
Borrowings maturity term				The asset-specific borrowings are term matched to the underlying collateral assets with an outside maturity date of May 20, 2020, which may be extended pursuant to two one-year extension options.
Secured debt agreements borrowings outstanding			$ 2,900,000,000	$ 2,900,000,000	$ 3,100,000,000		$ 3,100,000,000
GE Portfolio Acquisition Facility [Member] | Asset Specific Borrowings [Member] | Maximum [Member]
Debt Instrument [Line Items]
Percentage of guarantee rate						25.00%
Guarantee of outstanding borrowings						$ 250,000,000
Full Recourse Revolving Credit Facility [Member] | Barclays [Member] | Subsequent Events [Member]
Debt Instrument [Line Items]
Approximate credit line amount		$ 125,000,000
Maturity date		Apr. 04, 2018
Number of extension options | ExtensionOptions		2
Term of maturity date		1 year
Accrue interest rate, description		Accrue interest at a per annum pricing rate equal to the sum of (i) an applicable base rate or Eurodollar rate and (ii) an applicable margin, in each case, dependent on the applicable type of loan.
Maturity period		Subject to two one-year extension options, exercisable at our option.
LIBOR [Member] | Revolving Repurchase Facilities [Member] | Wells Fargo [Member]
Debt Instrument [Line Items]
Basis spread on debt obligation, in percent				1.78%
LIBOR [Member] | Revolving Repurchase Facilities [Member] | Bank of America [Member]
Debt Instrument [Line Items]
Basis spread on debt obligation, in percent				1.69%
LIBOR [Member] | Revolving Repurchase Facilities [Member] | MetLife [Member]
Debt Instrument [Line Items]
Basis spread on debt obligation, in percent				1.76%
LIBOR [Member] | Revolving Repurchase Facilities [Member] | Weighted-Average Cash Coupon [Member]
Debt Instrument [Line Items]
Basis spread on debt obligation, in percent				1.83%			1.82%
LIBOR [Member] | Revolving Repurchase Facilities [Member] | Weighted-Average All-in Cost of Credit [Member]
Debt Instrument [Line Items]
Basis spread on debt obligation, in percent				2.03%			2.04%
LIBOR [Member] | GE Portfolio Acquisition Facility [Member] | Sequential Repay Advance [Member]
Debt Instrument [Line Items]
Basis spread on debt obligation, in percent						3.10%
LIBOR basis spread on debt obligation				30-day LIBOR
Base Rate [Member] | GE Portfolio Acquisition Facility [Member] | Asset Specific Borrowings [Member] | Primary [Member]
Debt Instrument [Line Items]
Basis spread on debt obligation, in percent						1.75%
Base Rate [Member] | GE Portfolio Acquisition Facility [Member] | Asset Specific Borrowings [Member] | Primary [Member] | Year Four [Member]
Debt Instrument [Line Items]
Basis spread on debt obligation, in percent						1.80%
Base Rate [Member] | GE Portfolio Acquisition Facility [Member] | Asset Specific Borrowings [Member] | Primary [Member] | Year Five [Member]
Debt Instrument [Line Items]
Basis spread on debt obligation, in percent						1.85%