Other Assets and Liabilities - Additional Information (Detail) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021 USD ($) Loans	Mar. 31, 2021 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Jun. 30, 2021 USD ($) Loans	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)	Jan. 01, 2020 USD ($)	Dec. 31, 2019 USD ($)
CECL reserve	$ 128,945	$ 172,100	$ 178,050	$ 112,694	$ 128,945	$ 178,050	$ 173,549		$ 0
Increase (Decrease) in current expected credit loss reserve	(767)	(834)	(1,003)	4,677
Current expected credit loss reserve	$ 122	889	4,119	5,122	$ 122	4,119	1,723		0
Number of loans receivable | Loans	86				86
Credit Loss Reserve [Member]
CECL reserve	$ 122,000		4,100		$ 122,000	4,100
Increase (Decrease) in current expected credit loss reserve	(767,000)		(1,000)		(1,600)	3,700
Unfunded Loan Commitments [Member]
CECL reserve	4,037	$ 11,021	15,002	$ 22,536	4,037	15,002	$ 10,031		0
Increase (Decrease) in current expected credit loss reserve	$ (7,000)		$ (7,500)		$ (6,000)	11,700
Number of loans receivable | Loans	86				86
Unfunded loan commitments	$ 3,400,000				$ 3,400,000
Accounting Standards Update 2016-13 [Member]
CECL reserve								$ 13,942
Current expected credit loss reserve								445,000	$ 445
Accounting Standards Update 2016-13 [Member] | Unfunded Loan Commitments [Member]
CECL reserve	$ 3,300				3,300			$ 3,263
Increase (Decrease) in current expected credit loss reserve					$ 4,000	$ 15,000