AOCI (Reclassifications Out of Accumulated Other Comprehensive Income) (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018		Sep. 30, 2017
Reclassifications Out Of Accumulated Other Comprehensive Income
Income Before Income Taxes		$ 512	$ 1,489	$ 2,042		$ 2,379
Applicable income tax expense		79	475	321		694
Net income		433	1,014	1,721		1,685
ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember
Reclassifications Out Of Accumulated Other Comprehensive Income
Net income		(5)	(2)	(14)	[1]	3
Net Unrealized Gains On Available For Sale Securities
Reclassifications Out Of Accumulated Other Comprehensive Income
Reclassification adjustment for net losses (gains) included in net income		0	(1)	(9)		(3)
Income Before Income Taxes		0	(1)	(9)		(3)
Applicable income tax expense		0	0	2		1
Net income		0	(1)	(7)		(2)
Net Unrealized Gains On Available For Sale Securities | Net (Losses) Gains Included In Net Income
Reclassifications Out Of Accumulated Other Comprehensive Income
Reclassification adjustment for net losses (gains) included in net income		0	(1)	(9)		(3)
Net Unrealized Gains On Cash Flow Hedge Activities
Reclassifications Out Of Accumulated Other Comprehensive Income
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income		(2)	3	(2)		17
Income Before Income Taxes		(2)	3	(2)		17
Applicable income tax expense		0	(1)	0		(6)
Net income		(2)	2	(2)		11
Net Unrealized Gains On Cash Flow Hedge Activities | Interest Rate Contracts Related To C&I Loans
Reclassifications Out Of Accumulated Other Comprehensive Income
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income		(2)	3	(2)		17
Amortization Of Defined Benefit Pension Items
Reclassifications Out Of Accumulated Other Comprehensive Income
Income Before Income Taxes	[1]	(3)	(5)	(7)		(9)
Applicable income tax expense	[1]	0	2	2		3
Net income	[1]	(3)	(3)	(5)		(6)
Amortization Of Defined Benefit Pension Items | Net Actuarial Loss
Reclassifications Out Of Accumulated Other Comprehensive Income
Net periodic pension cost	[1],[2]	(1)	(2)	(5)		(6)
Amortization Of Defined Benefit Pension Items | Pension Settlement
Reclassifications Out Of Accumulated Other Comprehensive Income
Net periodic pension cost	[1],[2]	$ (2)	$ (3)	$ (2)		$ (3)

[1] Amounts in parentheses indicate reductions to net income

[2] This AOCI component is included in the computation of net periodic benefit cost. Refer to Note 21 of the Notes to Consolidated Financial Statements included in the Bancorp’s Annual Report on Form 10-K for the year ended December 31, 2017 for further information.