Collateral and Offsetting of Assets and Liabilities - Offsetting of Financial Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Derivative Liabilities:
Gross Amount Recognized	$ (10,069)	$ (6,006)
Counterparty netting	6,601	4,470
Cash collateral netting	2,855	1,164
Derivative liabilities, net	(613)	(372)
Gross Amount Not Offset in the Consolidated Balance Sheets	0	0
Net Amount	(613)	(372)
Securities Sold under Agreements to Repurchase [Abstract]
Gross Amount Recognized	(2,797)	(9,843)
Counterparty netting	2,797	9,843
Net Amount Presented in the Consolidated Balance Sheets	0	0
Gross Amount Not Offset in the Consolidated Balance Sheets	0	0
Net Amount	0	0
Offsetting Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned [Abstract]
Gross Amount Recognized	(12,866)	(15,849)
Counterparty netting	9,398	14,313
Cash collateral netting	2,855	1,164
Net Amount Presented in the Consolidated Balance Sheets	(613)	(372)
Gross Amount Not Offset in the Consolidated Balance Sheets	0	0
Net Amount	(613)	(372)
Other
Derivative Liabilities:
Gross Amount Recognized	(66)	(144)
Counterparty netting	0	0
Cash collateral netting	0	0
Derivative liabilities, net	(66)	(144)
Gross Amount Not Offset in the Consolidated Balance Sheets	0	0
Net Amount	(66)	(144)
OTC derivatives
Derivative Liabilities:
Gross Amount Recognized	(9,559)	(5,731)
Counterparty netting	6,600	4,465
Cash collateral netting	2,846	1,164
Derivative liabilities, net	(113)	(102)
Gross Amount Not Offset in the Consolidated Balance Sheets	0	0
Net Amount	(113)	(102)
Cleared and exchange-traded derivatives
Derivative Liabilities:
Gross Amount Recognized	(17)	(5)
Counterparty netting	1	5
Cash collateral netting	9	0
Derivative liabilities, net	(7)	0
Gross Amount Not Offset in the Consolidated Balance Sheets	0	0
Net Amount	(7)	0
Offsetting Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned [Abstract]
Aggregate fair value of securities posted	2,600	3,500
Commitments
Derivative Liabilities:
Gross Amount Recognized	(427)	(126)
Counterparty netting	0	0
Cash collateral netting	0	0
Derivative liabilities, net	(427)	(126)
Gross Amount Not Offset in the Consolidated Balance Sheets	0	0
Net Amount	(427)	(126)
Cash collateral posted
Offsetting Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned [Abstract]
Aggregate fair value of securities posted	600	200
Non cash collateral posted
Offsetting Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned [Abstract]
Aggregate fair value of securities posted	2,200	300
Securities Sold under Agreements to Repurchase
Offsetting Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned [Abstract]
Cash collateral netting	$ 0	$ 0