Loans Receivable, Net - Overall Statistics for Loans Receivable Portfolio (Parenthetical) (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Percentage of Portfolio	100.00%	100.00%
Additional loan receivable of floating rate	$ 17,060,102	$ 16,572,715
Prepayment Restrictions Including Yield Maintenance Lock Out Provisions [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Percentage of Portfolio	35.00%	31.00%
Without Prepayment Restrictions [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Percentage of Portfolio	65.00%	69.00%
Floating Rate Mortgage [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Percentage of Portfolio	99.50%	99.40%
Fixed Rate Mortgage [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Percentage of Portfolio	0.50%
Above Applicable Index Rate [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Additional loan receivable of floating rate	$ 14,000,000	$ 13,700,000