Loans Receivable, Net - Additional Information (Detail)	3 Months Ended					6 Months Ended
	Jun. 30, 2022 USD ($)	Mar. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted-average risk rating on loan exposure	2.8		2.8			2.8
Increase (decrease) in CECL reserve	$ 10,803,000	$ (2,458,000)		$ (43,155,000)	$ (1,449,000)
CECL reserve	133,024,000	$ 122,221,000	$ 124,679,000	128,945,000	$ 172,100,000	$ 133,024,000	$ 128,945,000	$ 173,549,000
Reversal of remaining CECL reserve	(12,983,000)			$ 50,906,000		(10,446,000)	52,199,000
Loans held	26,509,461,000		23,669,111,000			26,509,461,000
Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held	6,500,608,000		5,771,517,000			6,500,608,000
Multifamily | Joint Venture
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held	802,200,000		746,900,000			802,200,000
Multifamily Properties
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount of loans	37,500,000		37,500,000			37,500,000
Multifamily Asset in New York City
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in CECL reserve			14,800,000
CECL reserve	0					0
Principal charge-offs			14,400,000
Reversal of remaining CECL reserve			$ 360,000
Income recorded on loan							0
Hospitality Asset in New York City
Accounts, Notes, Loans and Financing Receivable [Line Items]
CECL reserve	54,900,000					54,900,000
Carrying amount of loans	$ 286,300,000					286,300,000
Income recorded on loan						$ 0	$ 0