Secured Debt Agreements, Net - Additional Information (Detail) € in Millions, £ in Millions		3 Months Ended			6 Months Ended					12 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($) ExtensionOptions	Jun. 30, 2017 USD ($) Facility	Jun. 30, 2017 GBP (£) Facility	Jun. 30, 2017 EUR (€) Facility	Dec. 31, 2016 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)	May 31, 2017 USD ($)
Debt Instrument [Line Items]
Basis spread on debt obligation, in percent					1.90%	1.90%	1.90%
Weighted-average advance rate					78.80%	78.80%	78.80%
Secured debt agreements borrowings outstanding	$ 5,806,037,000	$ 5,806,037,000			$ 5,806,037,000			$ 5,716,354,000		$ 5,716,354,000
Interest expense		54,352,000	$ 49,065,000		101,026,000				$ 94,446,000
Secured debt agreements borrowings outstanding	5,823,766,000	5,823,766,000			5,823,766,000			5,731,626,000		5,731,626,000
Covenants, minimum tangible net worth	$ 1,900,000,000	$ 1,900,000,000			$ 1,900,000,000
Covenants, percentage of tangible assets on cash proceeds from equity issuances					75.00%	75.00%	75.00%
Covenants, percentage of recourse indebtedness	5.00%	5.00%			5.00%
Maximum [Member]
Debt Instrument [Line Items]
Covenants, indebtedness to total assets, in percent	83.33%	83.33%			83.33%
Minimum [Member]
Debt Instrument [Line Items]
Covenants, EBITDA to fixed charges, in percent					140.00%	140.00%	140.00%
Covenants, minimum cash liquidity amount	$ 10,000,000	$ 10,000,000			$ 10,000,000
Asset-Specific Financings [Member]
Debt Instrument [Line Items]
Weighted-average outstanding balance					628,300,000			571,100,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Weighted-average outstanding balance					1,000,000			29,900,000
Interest expense					589,000			927,000
Amortization of deferred fees and expenses					332,000			255,000
Secured debt agreements borrowings outstanding	90,750,000	90,750,000			90,750,000			0		0
Revolving Credit Facility [Member] | Barclays [Member]
Debt Instrument [Line Items]
Maximum Facility Size	250,000,000	$ 250,000,000			250,000,000						$ 125,000,000
First mortgage bridge to term financing maximum period		6 months
GE Portfolio Acquisition Facility [Member]
Debt Instrument [Line Items]
Secured debt agreements borrowings outstanding	1,188,076,000	$ 1,188,076,000			1,188,076,000			1,479,582,000		1,479,582,000
GE Portfolio Acquisition Facility [Member] | Wells Fargo [Member]
Debt Instrument [Line Items]
Maximum Facility Size	1,300,000,000	1,300,000,000			1,300,000,000
Approximate credit line, outstanding amount	1,200,000,000
Amount available for potential future fundings of loan	142,600,000	142,600,000			$ 142,600,000
GE Portfolio Acquisition Facility [Member] | Asset Specific Borrowings [Member]
Debt Instrument [Line Items]
Weighted average rate				80.00%
Maturity date					May 20, 2020	May 20, 2020	May 20, 2020
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.	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.	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.
Number of extension options | ExtensionOptions				2
Term of maturity date				1 year
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
GE Portfolio Acquisition Facility [Member] | Weighted-Average All-in Cost of Credit [Member] | Asset Specific Borrowings [Member]
Debt Instrument [Line Items]
Secured debt agreements borrowings outstanding	1,200,000,000	1,200,000,000			$ 1,200,000,000			1,500,000,000		1,500,000,000
Credit Facilities [Member]
Debt Instrument [Line Items]
Number of revolving repurchase facilities closed | Facility					2	2	2
Additional credit capacity						£ 250.0	€ 250.0
Weighted-average outstanding balance					$ 3,800,000,000			2,800,000,000
Aggregate borrowings	4,000,000,000	4,000,000,000			$ 4,000,000,000			3,600,000,000		$ 3,600,000,000
Weighted-average advance rate					78.80%	78.80%	78.80%			79.10%
Weighted-average initial maturity					1 year 6 months	1 year 6 months	1 year 6 months			1 year 6 months
Maximum Facility Size	6,643,940,000	6,643,940,000			$ 6,643,940,000			5,479,180,000		$ 5,479,180,000
Amount available for potential future fundings of loan	487,374,000	487,374,000			487,374,000			541,743,000		541,743,000
Secured debt agreements borrowings outstanding	4,014,582,000	4,014,582,000			4,014,582,000			3,572,837,000		3,572,837,000
Credit Facilities [Member] | Wells Fargo [Member]
Debt Instrument [Line Items]
Maximum Facility Size	2,000,000,000	2,000,000,000			2,000,000,000			2,000,000,000		2,000,000,000
Amount available for potential future fundings of loan	$ 316,534,000	$ 316,534,000			$ 316,534,000			$ 232,209,000		$ 232,209,000
Borrowings maturity term					Term matched	Term matched	Term matched
Credit Facilities [Member] | Asset-Specific Financings [Member]
Debt Instrument [Line Items]
Additional credit capacity					$ 500,000,000
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%
LIBOR [Member] | GE Portfolio Acquisition Facility [Member] | Weighted-Average All-in Cost of Credit [Member] | Asset Specific Borrowings [Member]
Debt Instrument [Line Items]
Basis spread on debt obligation, in percent					1.80%	1.80%	1.80%			1.83%
LIBOR [Member] | Credit Facilities [Member] | Weighted-Average Cash Coupon [Member]
Debt Instrument [Line Items]
Basis spread on debt obligation, in percent					1.90%	1.90%	1.90%			1.82%
LIBOR [Member] | Credit Facilities [Member] | Weighted-Average All-in Cost of Credit [Member]
Debt Instrument [Line Items]
Basis spread on debt obligation, in percent					2.11%	2.11%	2.11%			2.02%