Loans Receivable, Net - Additional Information (Detail)		3 Months Ended	12 Months Ended
	Jul. 01, 2020 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jan. 01, 2020 USD ($)	Dec. 31, 2018 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted-average risk rating on loan exposure			2.8	3.0
CECL reserve			$ 124,679,000	$ 173,549,000	$ 0
Increase (decrease) in CECL reserve			(48,900,000)
Carrying Amount of Loans			22,003,017,000	16,572,715,000	16,164,801,000		$ 14,191,200,000
Principal charge-offs			14,427,000	0	0
CECL reserve			124,679,000	173,549,000	$ 0
Loans held			23,669,111,000	17,454,621,000
Reduction In Loan Spread And Extension In Maturity Date
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable troubled debt restructuring premodification recorded investment income	$ 0
COVID-19 pandemic
Accounts, Notes, Loans and Financing Receivable [Line Items]
CECL reserve						$ 13,900,000
Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held			5,771,517,000	1,862,667,000
Multifamily | Joint Venture
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held			746,900,000	$ 484,800,000
Multifamily Asset in New York City
Accounts, Notes, Loans and Financing Receivable [Line Items]
CECL reserve			0
Increase (decrease) in CECL reserve		$ 14,800,000	(360,000)
Hospitality Asset in New York City
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying Amount of Loans			286,300,000
CECL reserve			54,900,000
Multifamily Properties
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying Amount of Loans			37,500,000
Principal charge-offs			$ 14,400,000