Financial Derivatives (Derivative Assets and Liabilitites Offsetting) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Offsetting Derivative Assets [Abstract]
Derivative Asset, Gross Fair Value	$ 8,773	$ 3,502
Derivative Asset, Fair Value Offset Amount	1,341	690
Derivative Asset, Cash Collateral	2,110	616
Derivative Asset, Net	5,322	2,196
Derivative Asset, Securities Collateral Held Under Master Netting Agreements	635	215
Derivative Asset, Fair Value, Amount Offset Against Collateral	4,687	1,981
Offsetting Derivative Liabilities [Abstract]
Derivative Liability, Gross Fair Value	3,928	2,019
Derivative Liability, Fair Value Offset Amount	1,341	690
Derivative Liability, Cash Collateral	1,109	790
Derivative Liability, Net	1,478	539
Derivative Liability, Fair Value of Collateral
Derivative Liability, Fair Value, Amount Offset Against Collateral	1,478	539
Interest Rate Contracts [Member] | Over the Counter Cleared [Member]
Offsetting Derivative Assets [Abstract]
Derivative Asset, Gross Fair Value	296	14
Derivative Asset, Net	296	14
Derivative Asset, Fair Value, Amount Offset Against Collateral	296	14
Offsetting Derivative Liabilities [Abstract]
Derivative Liability, Gross Fair Value	194	14
Derivative Liability, Net	194	14
Derivative Liability, Fair Value, Amount Offset Against Collateral	194	14
Interest Rate Contracts [Member] | Over the Counter [Member]
Offsetting Derivative Assets [Abstract]
Derivative Asset, Gross Fair Value	6,809	2,969
Derivative Asset, Fair Value Offset Amount	499	365
Derivative Asset, Cash Collateral	1,701	593
Derivative Asset, Net	4,609	2,011
Derivative Asset, Securities Collateral Held Under Master Netting Agreements	634	215
Derivative Asset, Fair Value, Amount Offset Against Collateral	3,975	1,796
Offsetting Derivative Liabilities [Abstract]
Derivative Liability, Gross Fair Value	2,072	1,279
Derivative Liability, Fair Value Offset Amount	901	475
Derivative Liability, Cash Collateral	970	692
Derivative Liability, Net	201	112
Derivative Liability, Fair Value, Amount Offset Against Collateral	201	112
Commodity Contract [Member]
Offsetting Derivative Assets [Abstract]
Derivative Asset, Gross Fair Value	1,044	306
Derivative Asset, Fair Value Offset Amount	484	198
Derivative Asset, Cash Collateral	382	18
Derivative Asset, Net	178	90
Derivative Asset, Fair Value, Amount Offset Against Collateral	178	90
Offsetting Derivative Liabilities [Abstract]
Derivative Liability, Gross Fair Value	1,035	301
Derivative Liability, Fair Value Offset Amount	268	152
Derivative Liability, Cash Collateral	22	17
Derivative Liability, Net	745	132
Derivative Liability, Fair Value, Amount Offset Against Collateral	745	132
Foreign Exchange And Other Contract [Member]
Offsetting Derivative Assets [Abstract]
Derivative Asset, Gross Fair Value	624	213
Derivative Asset, Fair Value Offset Amount	358	127
Derivative Asset, Cash Collateral	27	5
Derivative Asset, Net	239	81
Derivative Asset, Securities Collateral Held Under Master Netting Agreements	1
Derivative Asset, Fair Value, Amount Offset Against Collateral	238	81
Offsetting Derivative Liabilities [Abstract]
Derivative Liability, Gross Fair Value	627	425
Derivative Liability, Fair Value Offset Amount	172	63
Derivative Liability, Cash Collateral	117	81
Derivative Liability, Net	338	281
Derivative Liability, Fair Value, Amount Offset Against Collateral	$ 338	$ 281