Financial Derivatives (Derivative Assets and Liabilities Offsetting) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Offsetting Derivative Assets [Abstract]
Derivative asset, gross fair value	$ 7,035	$ 6,533
Derivative Asset, Fair Value Offset Amount	1,027	720
Derivative asset, cash collateral	757	1,434
Derivative Asset, Net	5,251	4,379
Derivative Asset, Securities Collateral Held Under Master Netting Agreements	287	532
Derivative Asset, Fair Value, Amount Offset Against Collateral	4,964	3,847
Offsetting Derivative Liabilities [Abstract]
Derivative liability, gross fair value	4,781	2,756
Derivative liability, fair value offset amount	1,027	720
Derivative liability, cash collateral	2,403	1,452
Derivative liability, net	1,351	584
Derivative liability, fair value of collateral
Derivative liability, fair value, amount offset against collateral	1,351	584
Interest Rate Contracts | Over-the-counter cleared
Offsetting Derivative Assets [Abstract]
Derivative asset, gross fair value	51	48
Derivative Asset, Net	51	48
Derivative Asset, Fair Value, Amount Offset Against Collateral	51	48
Offsetting Derivative Liabilities [Abstract]
Derivative liability, gross fair value	68	42
Derivative liability, net	68	42
Derivative liability, fair value, amount offset against collateral	68	42
Interest Rate Contracts | Over-the-counter
Offsetting Derivative Assets [Abstract]
Derivative asset, gross fair value	4,219	5,803
Derivative Asset, Fair Value Offset Amount	556	430
Derivative asset, cash collateral	723	1,426
Derivative Asset, Net	2,940	3,947
Derivative Asset, Securities Collateral Held Under Master Netting Agreements	287	531
Derivative Asset, Fair Value, Amount Offset Against Collateral	2,653	3,416
Offsetting Derivative Liabilities [Abstract]
Derivative liability, gross fair value	1,647	1,740
Derivative liability, fair value offset amount	613	462
Derivative liability, cash collateral	813	1,179
Derivative liability, net	221	99
Derivative liability, fair value, amount offset against collateral	221	99
Commodity contracts:
Offsetting Derivative Assets [Abstract]
Derivative asset, gross fair value	2,521	411
Derivative Asset, Fair Value Offset Amount	343	209
Derivative asset, cash collateral	28	4
Derivative Asset, Net	2,150	198
Derivative Asset, Fair Value, Amount Offset Against Collateral	2,150	198
Offsetting Derivative Liabilities [Abstract]
Derivative liability, gross fair value	2,536	384
Derivative liability, fair value offset amount	353	182
Derivative liability, cash collateral	1,511	103
Derivative liability, net	672	99
Derivative liability, fair value, amount offset against collateral	672	99
Foreign exchange contracts and other
Offsetting Derivative Assets [Abstract]
Derivative asset, gross fair value	244	271
Derivative Asset, Fair Value Offset Amount	128	81
Derivative asset, cash collateral	6	4
Derivative Asset, Net	110	186
Derivative Asset, Securities Collateral Held Under Master Netting Agreements		1
Derivative Asset, Fair Value, Amount Offset Against Collateral	110	185
Offsetting Derivative Liabilities [Abstract]
Derivative liability, gross fair value	530	590
Derivative liability, fair value offset amount	61	76
Derivative liability, cash collateral	79	170
Derivative liability, net	390	344
Derivative liability, fair value, amount offset against collateral	$ 390	$ 344