Derivative Instruments (Offsetting Assets and Liabilities) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Derivative Assets
Gross Amounts of Recognized Financial Instruments	$ 34,905	$ 14,303
Gross Amounts Offset in the Statements of Financial Position	(31,880)	(13,519)
Net Amounts Presented in the Statements of Financial Position	3,025	784
Financial Instruments/Collateral	(2,109)	(607)
Net Amount	916	177
Securities purchased under agreement to resell
Gross Amounts of Recognized Financial Instruments	325	1,012
Gross Amounts Offset in the Statements of Financial Position	0	0
Net Amounts Presented in the Statements of Financial Position	325	1,012
Financial Instruments/Collateral	(325)	(1,012)
Net Amount	0	0
Total assets
Gross Amounts of Recognized Financial Instruments	35,230	15,315
Gross Amounts Offset in the Statements of Financial Position	(31,880)	(13,519)
Net Amounts Presented in the Statements of Financial Position	3,350	1,796
Financial Instruments/Collateral	(2,434)	(1,619)
Net Amount	916	177
Derivative Liabilities
Gross Amounts of Recognized Financial Instruments	13,259	7,528
Gross Amounts Offset in the Statements of Financial Position	(12,381)	(6,705)
Net Amounts Presented in the Statements of Financial Position	878	823
Financial Instruments/Collateral	(9)	(244)
Net Amount	869	579
Securities sold under agreement to repurchase
Gross Amounts of Recognized Financial Instruments	10,557	9,681
Gross Amounts Offset in the Statements of Financial Position	0	0
Net Amounts Presented in the Statements of Financial Position	10,557	9,681
Financial Instruments/Collateral	(10,557)	(9,681)
Net Amount	0	0
Total liabilities
Gross Amounts of Recognized Financial Instruments	23,816	17,209
Gross Amounts Offset in the Statements of Financial Position	(12,381)	(6,705)
Net Amounts Presented in the Statements of Financial Position	11,435	10,504
Financial Instruments/Collateral	(10,566)	(9,925)
Net Amount	$ 869	$ 579