Other Assets and Liabilities - Summary Of Current Expected Credit Loss Reserve By Pool (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Current Expected Credit Loss Reserve	$ 1,723	$ 0
Increase (Decrease) in current expected credit loss reserve	(834)	4,677
Current Expected Credit Loss Reserve	889	5,122
U.S. Loans [Member]
Current Expected Credit Loss Reserve	1,723	0
Increase (Decrease) in current expected credit loss reserve	(834)	4,677
Current Expected Credit Loss Reserve	889	5,122
Non-U.S. Loans [Member]
Current Expected Credit Loss Reserve	0	0
Increase (Decrease) in current expected credit loss reserve	0	0
Current Expected Credit Loss Reserve	0	0
Unique Loans [Member]
Increase (Decrease) in current expected credit loss reserve	0	0
Current Expected Credit Loss Reserve	0	0
Impaired Loans [Member]
Current Expected Credit Loss Reserve	0	0
Increase (Decrease) in current expected credit loss reserve	0	0
Current Expected Credit Loss Reserve	0	0
Accounting Standards Update 2016-13 [Member]
Current Expected Credit Loss Reserve		445
Accounting Standards Update 2016-13 [Member] | U.S. Loans [Member]
Current Expected Credit Loss Reserve		445
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	0
Accounting Standards Update 2016-13 [Member] | Impaired Loans [Member]
Current Expected Credit Loss Reserve		$ 0