Other Assets and Liabilities - Additional Information (Detail)	3 Months Ended	6 Months Ended
	Jun. 30, 2020 USD ($) Loans	Jun. 30, 2020 USD ($) Loans	Mar. 31, 2020 USD ($)	Jan. 01, 2020 USD ($)	Dec. 31, 2019 USD ($)
CECL reserve	$ 178,050,000	$ 178,050,000	$ 112,694,000		$ 0
Increase (Decrease) in current expected credit loss reserve	(1,003,000)	3,674,000
Current expected credit loss reserve	$ 4,119,000	$ 4,119,000	5,122,000		0
Number of loans receivable | Loans	91	91
Credit Loss Reserve [Member]
CECL reserve	$ 4,100,000	$ 4,100,000
Increase (Decrease) in current expected credit loss reserve	1,000,000.0	3,700,000
Unfunded Loan Commitments [Member]
CECL reserve	15,002,000	15,002,000	$ 22,536,000		0
Increase (Decrease) in current expected credit loss reserve	$ 7,500,000	$ 11,700,000
Number of loans receivable | Loans	91	91
Unfunded loan commitments	$ 3,600,000,000	$ 3,600,000,000
Accounting Standards Update 2016-13 [Member]
CECL reserve				$ 13,942,000
Current expected credit loss reserve	445,000	445,000			$ 445,000
Accounting Standards Update 2016-13 [Member] | Unfunded Loan Commitments [Member]
CECL reserve	$ 3,300,000	3,300,000		$ 3,263,000
Increase (Decrease) in current expected credit loss reserve		$ 15,000,000.0