Other Assets and Liabilities - Summary Of Current Expected Credit Loss Reserve By Pool (Detail)	12 Months Ended
	Dec. 31, 2020 USD ($)
Current Expected Credit Loss Reserve	$ 0
Increase (Decrease) in current expected credit loss reserve	1,278,000
Current Expected Credit Loss Reserve	1,723,000
U.S. Loans [Member]
Current Expected Credit Loss Reserve	0
Increase (Decrease) in current expected credit loss reserve	1,278,000
Current Expected Credit Loss Reserve	1,723,000
Non-U.S. Loans [Member]
Current Expected Credit Loss Reserve	0
Increase (Decrease) in current expected credit loss reserve	0
Current Expected Credit Loss Reserve	0
Unique Loans [Member]
Current Expected Credit Loss Reserve	0
Increase (Decrease) in current expected credit loss reserve	0
Current Expected Credit Loss Reserve	0
Impaired Loans [Member]
Current Expected Credit Loss Reserve	0
Increase (Decrease) in current expected credit loss reserve	0
Current Expected Credit Loss Reserve	0
Accounting Standards Update 2016-13 [Member]
Current Expected Credit Loss Reserve	445,000
Current Expected Credit Loss Reserve	445,000
Accounting Standards Update 2016-13 [Member] | U.S. Loans [Member]
Current Expected Credit Loss Reserve	445,000
Accounting Standards Update 2016-13 [Member] | Non-U.S. Loans [Member]
Current Expected Credit Loss Reserve	0
Accounting Standards Update 2016-13 [Member] | Unique Loans [Member]
Current Expected Credit Loss Reserve	0
Accounting Standards Update 2016-13 [Member] | Impaired Loans [Member]
Current Expected Credit Loss Reserve	$ 0