Schedule IV - Mortgage Loans on Real Estate Footnotes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Tax basis of loans	$ 21,300,000
Principal charge-offs	14,427	$ 0	$ 0
Outstanding principal amount	22,003,017	16,572,715	16,164,801	$ 14,191,200
CECL reserve	124,679	$ 173,549	$ 0
Multifamily Properties
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal charge-offs	14,400
Outstanding principal amount	37,500
Hospitality Asset in New York City
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Outstanding principal amount	286,300
CECL reserve	$ 54,900