Financial Derivatives (Derivative Assets and Liabilitites Offsetting) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Offsetting Derivative Assets [Abstract]
Derivative Asset, Gross Fair Value	$ 4,638	$ 2,081
Derivative Asset, Fair Value Offset Amount	890	688
Derivative Asset, Cash Collateral	914	341
Derivative Asset, Net	2,834	1,052
Derivative Asset, Securities Collateral Held Under Master Netting Agreements	298	25
Derivative Asset, Fair Value, Amount Offset Against Collateral	2,536	1,027
Offsetting Derivative Liabilities [Abstract]
Derivative Liability, Gross Fair Value	2,332	2,290
Derivative Liability, Fair Value Offset Amount	890	688
Derivative Liability, Cash Collateral	770	539
Derivative Liability, Net	672	1,063
Derivative Liability, Fair Value of Collateral		11
Derivative Liability, Fair Value, Amount Offset Against Collateral	672	1,052
Interest Rate Contracts [Member] | Over the Counter Cleared [Member]
Offsetting Derivative Assets [Abstract]
Derivative Asset, Gross Fair Value	24	29
Derivative Asset, Net	24	29
Derivative Asset, Fair Value, Amount Offset Against Collateral	24	29
Offsetting Derivative Liabilities [Abstract]
Derivative Liability, Gross Fair Value	26	24
Derivative Liability, Net	26	24
Derivative Liability, Fair Value, Amount Offset Against Collateral	26	24
Interest Rate Contracts [Member] | Over the Counter [Member]
Offsetting Derivative Assets [Abstract]
Derivative Asset, Gross Fair Value	3,870	1,472
Derivative Asset, Fair Value Offset Amount	399	450
Derivative Asset, Cash Collateral	848	117
Derivative Asset, Net	2,623	905
Derivative Asset, Securities Collateral Held Under Master Netting Agreements	297	25
Derivative Asset, Fair Value, Amount Offset Against Collateral	2,326	880
Offsetting Derivative Liabilities [Abstract]
Derivative Liability, Gross Fair Value	1,484	1,496
Derivative Liability, Fair Value Offset Amount	648	557
Derivative Liability, Cash Collateral	722	489
Derivative Liability, Net	114	450
Derivative Liability, Fair Value of Collateral		11
Derivative Liability, Fair Value, Amount Offset Against Collateral	114	439
Commodity Contract [Member]
Offsetting Derivative Assets [Abstract]
Derivative Asset, Gross Fair Value	381	311
Derivative Asset, Fair Value Offset Amount	244	76
Derivative Asset, Cash Collateral	58	210
Derivative Asset, Net	79	25
Derivative Asset, Fair Value, Amount Offset Against Collateral	79	25
Offsetting Derivative Liabilities [Abstract]
Derivative Liability, Gross Fair Value	377	305
Derivative Liability, Fair Value Offset Amount	163	56
Derivative Liability, Cash Collateral	2	17
Derivative Liability, Net	212	232
Derivative Liability, Fair Value, Amount Offset Against Collateral	212	232
Foreign Exchange And Other Contract [Member]
Offsetting Derivative Assets [Abstract]
Derivative Asset, Gross Fair Value	363	269
Derivative Asset, Fair Value Offset Amount	247	162
Derivative Asset, Cash Collateral	8	14
Derivative Asset, Net	108	93
Derivative Asset, Securities Collateral Held Under Master Netting Agreements	1
Derivative Asset, Fair Value, Amount Offset Against Collateral	107	93
Offsetting Derivative Liabilities [Abstract]
Derivative Liability, Gross Fair Value	445	465
Derivative Liability, Fair Value Offset Amount	79	75
Derivative Liability, Cash Collateral	46	33
Derivative Liability, Net	320	357
Derivative Liability, Fair Value, Amount Offset Against Collateral	$ 320	$ 357