Financial Derivatives (Derivative Assets and Liabilitites Offsetting) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Offsetting Derivative Assets [Abstract]
Derivative Asset, Gross Fair Value	$ 3,546	$ 2,081
Derivative Asset, Fair Value Offset Amount	642	688
Derivative Asset, Cash Collateral	673	341
Derivative Asset, Net	2,231	1,052
Derivative Asset, Securities Collateral Held Under Master Netting Agreements	176	25
Derivative Asset, Fair Value, Amount Offset Against Collateral	2,055	1,027
Offsetting Derivative Liabilities [Abstract]
Derivative Liability, Gross Fair Value	2,002	2,290
Derivative Liability, Fair Value Offset Amount	642	688
Derivative Liability, Cash Collateral	756	539
Derivative Liability, Net	604	1,063
Derivative Liability, Fair Value of Collateral		11
Derivative Liability, Fair Value, Amount Offset Against Collateral	604	1,052
Interest Rate Contracts [Member] | Over the Counter Cleared [Member]
Offsetting Derivative Assets [Abstract]
Derivative Asset, Gross Fair Value	23	29
Derivative Asset, Net	23	29
Derivative Asset, Fair Value, Amount Offset Against Collateral	23	29
Offsetting Derivative Liabilities [Abstract]
Derivative Liability, Gross Fair Value	28	24
Derivative Liability, Net	28	24
Derivative Liability, Fair Value, Amount Offset Against Collateral	28	24
Interest Rate Contracts [Member] | Over the Counter [Member]
Offsetting Derivative Assets [Abstract]
Derivative Asset, Gross Fair Value	3,089	1,472
Derivative Asset, Fair Value Offset Amount	383	450
Derivative Asset, Cash Collateral	638	117
Derivative Asset, Net	2,068	905
Derivative Asset, Securities Collateral Held Under Master Netting Agreements	176	25
Derivative Asset, Fair Value, Amount Offset Against Collateral	1,892	880
Offsetting Derivative Liabilities [Abstract]
Derivative Liability, Gross Fair Value	1,355	1,496
Derivative Liability, Fair Value Offset Amount	514	557
Derivative Liability, Cash Collateral	695	489
Derivative Liability, Net	146	450
Derivative Liability, Fair Value of Collateral		11
Derivative Liability, Fair Value, Amount Offset Against Collateral	146	439
Commodity Contract [Member]
Offsetting Derivative Assets [Abstract]
Derivative Asset, Gross Fair Value	221	311
Derivative Asset, Fair Value Offset Amount	134	76
Derivative Asset, Cash Collateral	32	210
Derivative Asset, Net	55	25
Derivative Asset, Fair Value, Amount Offset Against Collateral	55	25
Offsetting Derivative Liabilities [Abstract]
Derivative Liability, Gross Fair Value	217	305
Derivative Liability, Fair Value Offset Amount	73	56
Derivative Liability, Cash Collateral	1	17
Derivative Liability, Net	143	232
Derivative Liability, Fair Value, Amount Offset Against Collateral	143	232
Foreign Exchange And Other Contract [Member]
Offsetting Derivative Assets [Abstract]
Derivative Asset, Gross Fair Value	213	269
Derivative Asset, Fair Value Offset Amount	125	162
Derivative Asset, Cash Collateral	3	14
Derivative Asset, Net	85	93
Derivative Asset, Fair Value, Amount Offset Against Collateral	85	93
Offsetting Derivative Liabilities [Abstract]
Derivative Liability, Gross Fair Value	402	465
Derivative Liability, Fair Value Offset Amount	55	75
Derivative Liability, Cash Collateral	60	33
Derivative Liability, Net	287	357
Derivative Liability, Fair Value, Amount Offset Against Collateral	$ 287	$ 357