Loans Receivable, Net - Additional Information (Detail)	3 Months Ended							9 Months Ended
	Sep. 30, 2022 USD ($)	Jun. 30, 2022 USD ($)	Mar. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Sep. 30, 2022 USD ($)	Sep. 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	$ 11,407,000	$ 10,803,000	$ (2,458,000)		$ 1,443,000	$ (43,155,000)	$ (1,449,000)
CECL reserve	144,431,000	$ 133,024,000	$ 122,221,000	$ 124,679,000	130,388,000	$ 128,945,000	$ 172,100,000	$ 144,431,000	$ 130,388,000	$ 173,549,000
Reversal of remaining CECL reserve	(12,248,000)				$ (2,767,000)			(22,694,000)	49,432,000
Loans held	26,136,006,000			23,669,111,000				26,136,006,000
Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held	6,313,319,000			5,771,517,000				6,313,319,000
Multifamily | Joint Venture
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held	802,900,000			746,900,000				802,900,000
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