Loans, Lending Commitments and Related Allowance for Credit Losses - Allowance for Credit Losses Rollforward - Loans and Lending Commitments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Allowance for loan losses rollforward
Beginning balance	$ 835	$ 349
Effect of CECL adoption		9
Gross charge-offs	(10)	(32)
Provision (release) for credit losses	(58)	292
Other	(5)	(1)
Ending balance	762	617
Allowance for lending commitments rollforward
Beginning balance	396	241
Effect of CECL adoption		(50)
Provision (release)	(40)	115
Other	(2)	(2)
Ending balance	354	304
Corporate
Allowance for loan losses rollforward
Beginning balance	309	115
Effect of CECL adoption		(2)
Gross charge-offs	(1)	(32)
Provision (release) for credit losses	(56)	177
Other	(2)	0
Ending balance	250	258
Allowance for lending commitments rollforward
Beginning balance	323	201
Effect of CECL adoption		(41)
Provision (release)	(33)	91
Other	(1)	(2)
Ending balance	289	249
Secured lending facilities
Allowance for loan losses rollforward
Beginning balance	198	101
Effect of CECL adoption		(42)
Gross charge-offs	0	0
Provision (release) for credit losses	(3)	29
Other	(2)	0
Ending balance	193	88
Allowance for lending commitments rollforward
Beginning balance	38	27
Effect of CECL adoption		(11)
Provision (release)	(4)	16
Other	1	0
Ending balance	35	32
Commercial real estate
Allowance for loan losses rollforward
Beginning balance	211	75
Effect of CECL adoption		34
Gross charge-offs	(9)	0
Provision (release) for credit losses	5	66
Other	(1)	(1)
Ending balance	206	174
Allowance for lending commitments rollforward
Beginning balance	11	7
Effect of CECL adoption		1
Provision (release)	(2)	5
Other	(1)	0
Ending balance	8	13
Residential real estate
Allowance for loan losses rollforward
Beginning balance	59	25
Effect of CECL adoption		21
Gross charge-offs	0	0
Provision (release) for credit losses	(5)	1
Other	0	0
Ending balance	54	47
Allowance for lending commitments rollforward
Beginning balance	1	0
Effect of CECL adoption		2
Provision (release)	0	0
Other	0	0
Ending balance	1	2
SBL and Other
Allowance for loan losses rollforward
Beginning balance	58	33
Effect of CECL adoption		(2)
Gross charge-offs	0	0
Provision (release) for credit losses	1	19
Other	0	0
Ending balance	59	50
Allowance for lending commitments rollforward
Beginning balance	23	6
Effect of CECL adoption		(1)
Provision (release)	(1)	3
Other	(1)	0
Ending balance	$ 21	$ 8