AOCI - Reclassifications Out of AOCI (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Reclassifications Out Of Accumulated Other Comprehensive Income [Line Items]
Income Before Income Taxes	$ 577	$ 748	$ 1,572	$ 1,630
Applicable income tax expense	124	146	344	327
Net income	453	602	1,228	1,303
ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember
Reclassifications Out Of Accumulated Other Comprehensive Income [Line Items]
Net income	(2)	(1)	(6)	(8)
Net Unrealized Gains On Available For Sale Securities
Reclassifications Out Of Accumulated Other Comprehensive Income [Line Items]
Reclassification adjustment for net losses (gains) included in net income	0	0	1	(9)
Income Before Income Taxes	0	0	(1)	(9)
Applicable income tax expense	0	0	0	2
Net income	0	0	(1)	(7)
Net Unrealized Gains On Available For Sale Securities | Net (Losses) Gains Included In Net Income
Reclassifications Out Of Accumulated Other Comprehensive Income [Line Items]
Reclassification adjustment for net losses (gains) included in net income	0	0	(1)	(9)
Net Unrealized Gains On Cash Flow Hedge Activities
Reclassifications Out Of Accumulated Other Comprehensive Income [Line Items]
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	(1)	0	(3)	1
Income Before Income Taxes	(1)	0	(3)	1
Applicable income tax expense	0	0	0	0
Net income	(1)	0	(3)	1
Net Unrealized Gains On Cash Flow Hedge Activities | Interest Rate Contracts Related To C&I Loans
Reclassifications Out Of Accumulated Other Comprehensive Income [Line Items]
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	(1)	0	(3)	1
Amortization Of Defined Benefit Pension Items
Reclassifications Out Of Accumulated Other Comprehensive Income [Line Items]
Income Before Income Taxes	(1)	(1)	(2)	(2)
Applicable income tax expense	0	0	0	0
Net income	(1)	(1)	(2)	(2)
Amortization Of Defined Benefit Pension Items | Net Actuarial Loss
Reclassifications Out Of Accumulated Other Comprehensive Income [Line Items]
Net periodic pension cost	$ (1)	$ (1)	$ (2)	$ (2)