Reclassifications Out of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Reclassifications Out Of Accumulated Other Comprehensive Income [Line Items]
Income Before Income Taxes		$ 515	$ 464	$ 1,417	$ 1,509
Applicable income tax expense		134	124	367	411
Net income		381	340	1,056	1,096
Total Reclassifications For The Period
Reclassifications Out Of Accumulated Other Comprehensive Income [Line Items]
Net income		18	9	39	33
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		10	5	16	25
Net Unrealized Gains On Available For Sale Securities | Net Losses Included In Net Income
Reclassifications Out Of Accumulated Other Comprehensive Income [Line Items]
Reclassification adjustment for net losses (gains) included in net income	[1]	10	5	16	25
Income Before Income Taxes	[1]	10	5	16	25
Applicable income tax expense	[1]	(3)	(2)	(5)	(9)
Net income	[1]	7	3	11	16
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		20	10	55	31
Income Before Income Taxes	[1]	20	10	55	31
Applicable income tax expense	[1]	(7)	(3)	(19)	(11)
Net income	[1]	13	7	36	20
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]	20	10	55	31
Amortization Of Defined Benefit Pension Items | Net Actuarial Loss
Reclassifications Out Of Accumulated Other Comprehensive Income [Line Items]
Net periodic pension cost	[1],[2]	(2)	(2)	(7)	(5)
Income Before Income Taxes	[1]	(3)	(2)	(12)	(5)
Applicable income tax expense	[1]	1	1	4	2
Net income	[1]	(2)	$ (1)	(8)	$ (3)
Amortization Of Defined Benefit Pension Items | Pension Settlement
Reclassifications Out Of Accumulated Other Comprehensive Income [Line Items]
Net periodic pension cost	[1],[2]	$ (1)		$ (5)

[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 in the Bancorp’s Annual Report on Form 10-K for the year ended December 31, 2014 for information on the computation of net periodic benefit cost.