Secured Debt Agreements, Net - Additional Information (Detail)	3 Months Ended		6 Months Ended			12 Months Ended
	Jun. 30, 2020 USD ($) Lenders	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Debt Instrument [Line Items]
Aggregate borrowings	$ 9,431,109,000		$ 9,431,109,000	$ 9,753,059,000		$ 9,753,059,000
Interest expense	84,853,000	$ 116,891,000	189,092,000		$ 235,579,000
Covenants, minimum tangible net worth	$ 3,000,000,000.0		$ 3,000,000,000.0
Covenants, percentage of tangible assets on cash proceeds from equity issuances			75.00%
Covenants, percentage of recourse indebtedness	5.00%		5.00%
Maximum [Member]
Debt Instrument [Line Items]
Covenants, indebtedness to total assets, in percent	83.33%		83.33%
Minimum [Member]
Debt Instrument [Line Items]
Covenants, EBITDA to fixed charges, in percent			1.40%
Covenants, minimum cash liquidity amount	$ 10,000,000.0		$ 10,000,000.0
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Interest expense			901,000,000,000	972,000,000,000
Amortization of deferred fees and expenses			459,000,000,000	525,000,000,000
Revolving Credit Facility [Member] | Barclays [Member]
Debt Instrument [Line Items]
Maximum Facility Size	$ 250,000,000.0		250,000,000.0
Credit Facilities [Member]
Debt Instrument [Line Items]
Number of lenders | Lenders	7
Additional credit capacity	$ 7,900,000,000
Weighted-average outstanding balance			9,200,000,000	8,900,000,000
Aggregate borrowings	9,431,109,000		$ 9,431,109,000	9,800,000,000		$ 9,800,000,000
Basis spread on debt obligation, in percent						1.60%
Weighted-average advance rate			75.60%			79.40%
Weighted-average future funding period			3 years 4 months 24 days			3 years 7 months 6 days
Credit Facilities [Member] | Barclays [Member]
Debt Instrument [Line Items]
Aggregate borrowings	$ 1,607,267,000		$ 1,607,267,000	1,442,083,000		$ 1,442,083,000
Asset-Specific Financings [Member]
Debt Instrument [Line Items]
Weighted-average outstanding balance			$ 312,500,000	$ 262,500,000
LIBOR [Member] | Credit Facilities [Member] | Weighted-Average Cash Coupon [Member]
Debt Instrument [Line Items]
Basis spread on debt obligation, in percent			1.62%
LIBOR [Member] | Credit Facilities [Member] | Weighted-Average All-in Cost of Credit [Member]
Debt Instrument [Line Items]
Basis spread on debt obligation, in percent			1.82%			1.79%