Secured Debt, Net - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Debt Instrument [Line Items]
Interest expense	$ 82,690,000	$ 78,978,000	$ 243,413,000		$ 268,070,000
Covenants, minimum tangible net worth	$ 3,200,000,000		$ 3,200,000,000
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			925,000	$ 1,100,000
Amortization of deferred fees and expenses			262,000	411,000
Revolving Credit Facility [Member] | Acquisition Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, remaining borrowing capacity	146,300,000		146,300,000
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]
Collateral Assets	15,258,991,000		15,258,991,000	$ 12,040,907,000
Line of credit facility, remaining borrowing capacity	306,200,000,000		306,200,000,000
Credit Facilities Six [Member]
Debt Instrument [Line Items]
Potential	2,800,000,000		2,800,000,000
Collateral Assets	3,500,000,000		3,500,000,000
Credit Facilities Eight [Member] | One of the Secured Credit Facilities [Member]
Debt Instrument [Line Items]
Additional credit capacity	150,000,000.0
Credit Facilities Eight [Member] | Four of the Eight Secured Credit Facilities [Member]
Debt Instrument [Line Items]
Maximum Facility Size	$ 2,300,000,000		$ 2,300,000,000