Secured Debt Agreements, Net - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2019 USD ($) Facility	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Aggregate borrowings	$ 9,753,059,000	$ 1,839,698,000
Secured debt agreements borrowings outstanding	736,142,000
Interest expense	458,503,000	359,625,000	$ 234,870,000
Covenants, minimum tangible net worth	$ 2,800,000,000
Covenants, percentage of tangible assets on cash proceeds from equity issuances	75.00%
Covenants, percentage of recourse indebtedness	5.00%
Maximum [Member]
Debt Instrument [Line Items]
Covenants, indebtedness to total assets, in percent	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
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Weighted-average outstanding balance	14,300,000	44,300,000
Secured debt agreements borrowings outstanding		43,800,000
Interest expense	2,600,000	3,800,000
Amortization of deferred fees and expenses	1,000,000.0	1,100,000
Revolving Credit Facility [Member] | Barclays [Member]
Debt Instrument [Line Items]
Maximum Facility Size	250,000,000.0
Credit Facilities [Member]
Debt Instrument [Line Items]
Weighted-average outstanding balance	8,800,000,000	6,500,000,000
Aggregate borrowings	$ 9,753,059,000	$ 8,870,897,000
Basis spread on debt obligation, in percent		1.72%
Weighted-average advance rate	79.40%	79.50%
Weighted-average initial maturity	3 years 7 months 6 days	3 years 6 months
Credit Facilities [Member] | Barclays [Member]
Debt Instrument [Line Items]
Aggregate borrowings	$ 1,442,083,000	$ 890,620,000
Asset-Specific Financings [Member]
Debt Instrument [Line Items]
Weighted-average outstanding balance	$ 185,000,000.0	$ 52,800,000
Credit Facilities One [Member] | Joint Venture [Member]
Debt Instrument [Line Items]
Number of new credit facility | Facility	6
Additional credit capacity	$ 2,900,000,000
Credit Facilities Two [Member] | Joint Venture [Member]
Debt Instrument [Line Items]
Number of new credit facility | Facility	2
Additional credit capacity	$ 577,000,000.0
LIBOR [Member] | Credit Facilities [Member] | Weighted-Average Cash Coupon [Member]
Debt Instrument [Line Items]
Basis spread on debt obligation, in percent	1.60%
LIBOR [Member] | Credit Facilities [Member] | Weighted-Average All-in Cost of Credit [Member]
Debt Instrument [Line Items]
Basis spread on debt obligation, in percent	1.79%	1.90%