Other Assets and Liabilities - Summary Of Current Expected Credit Loss Reserve By Pool (Detail) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Current Expected Credit Loss Reserve	$ 889	$ 1,723	$ 5,122	$ 0	$ 1,723	$ 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
U.S. Loans [Member]
Current Expected Credit Loss Reserve	889	1,723	5,122	0	1,723	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
Non-U.S. Loans [Member]
Current Expected Credit Loss Reserve	0	0	0	0	0	0
Increase (Decrease) in current expected credit loss reserve	0	0	0	0
Current Expected Credit Loss Reserve	0	0	0	0	0	0
Unique Loans [Member]
Current Expected Credit Loss Reserve	0	0	0	0	0	0
Increase (Decrease) in current expected credit loss reserve	0	0	0	0
Current Expected Credit Loss Reserve	0	0	0	0	0	0
Impaired Loans [Member]
Current Expected Credit Loss Reserve	0	0	0	0	0	0
Increase (Decrease) in current expected credit loss reserve	0	0	0	0
Current Expected Credit Loss Reserve	$ 0	$ 0	$ 0	0	$ 0	0
Accounting Standards Update 2016-13 [Member]
Current Expected Credit Loss Reserve				445		445
Accounting Standards Update 2016-13 [Member] | U.S. Loans [Member]
Current Expected Credit Loss Reserve				445		445
Accounting Standards Update 2016-13 [Member] | Non-U.S. Loans [Member]
Current Expected Credit Loss Reserve				0		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		$ 0