AOCI (Activity of the Components of Other Comprehensive Income and 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, 2018	Sep. 30, 2017
Net activity for accumulated net unrealized gain (loss) on available-for-sale securities
Unrealized holding gains (losses) on available-for-sale securities arising during period	$ (207)	$ 22	$ (834)			$ 130
Reclassification adjustment for net (gains) losses included in net income	0	1	7			2
Net activity for net unrealized gain (loss) on cash flow hedge derivatives
Unrealized holding gains (losses) on cash flow hedge derivatives arising during period	(19)	0	(24)			2
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	2	(2)	2			(11)
Net activity for defined benefit plans, net
Net actuarial gain (loss) arising during the period	2	2	2			3
Reclassification of amounts to net periodic benefit costs	(3)	(3)	(5)			(6)
Total Other Comprehensive Activity
Pre-tax activity total	(293)	34	(1,097)			198
Total, Tax	70	(12)	251			(72)
Other comprehensive income (loss)	(223)	22	(846)		$ (846)	126
Total Accumulated Other Comprehensive Income
Total Accumulated Other Comprehensive Income - Beginning Balance	(552)	163	73	[1]		59
Other comprehensive income (loss), Net of Tax	(223)	22	(846)		(846)	126
Total Accumulated Other Comprehensive Income - Ending Balance	(775)	185	(775)		(775)	185
Accumulated Net Unrealized Investment Gain (Loss)
Pre-tax activity for accumulated net unrealized gain (loss) on available-for-sale securities
Unrealized holding gains (losses) on available-for-sale securities arising during period	(271)	34	(1,082)			204
Reclassification adjustment for net losses (gains) included in net income	0	1	9			3
Net unrealized gains on available-for-sale securities	(271)	35	(1,073)			207
Tax effect for accumulated net unrealized gain (loss) on available-for-sale securities
Unrealized holding gains (losses) on available-for-sale securities arising during period	64	(12)	248			(74)
Reclassification adjustment for net losses (gains) included in net income	0	0	(2)			(1)
Net unrealized gains on available-for-sale securities	64	(12)	246			(75)
Net activity for accumulated net unrealized gain (loss) on available-for-sale securities
Unrealized holding gains (losses) on available-for-sale securities arising during period	(207)	22	(834)			130
Reclassification adjustment for net (gains) losses included in net income	0	1	7			2
Net unrealized gains on available-for-sale securities	(207)	23	(827)			132
Total Other Comprehensive Activity
Other comprehensive income (loss)	(207)	23	(827)			132
Total Accumulated Other Comprehensive Income
Total Accumulated Other Comprehensive Income - Beginning Balance	(485)	210	135	[1]		101
Other comprehensive income (loss), Net of Tax	(207)	23	(827)			132
Total Accumulated Other Comprehensive Income - Ending Balance	(692)	233	(692)		(692)	233
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges
Pre-tax activity for net unrealized gain (loss) on cash flow hedge derivatives
Unrealized holding gains (losses) on cash flow hedge derivatives arising during period	(25)	0	(31)			3
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	2	(3)	2			(17)
Net unrealized gains on cash flow hedge derivatives	(23)	(3)	(29)			(14)
Tax effect for net unrealized gain (loss) on cash flow hedge derivatives
Unrealized holding gains (losses) on cash flow hedge derivatives arising during period	6	0	7			(1)
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	0	1	0			6
Net unrealized gains on cash flow hedge derivatives	6	1	7			5
Net activity for net unrealized gain (loss) on cash flow hedge derivatives
Unrealized holding gains (losses) on cash flow hedge derivatives arising during period	(19)	0	(24)			2
Reclassification adjustment for net gains on cash flow hedge derivatives included in net income	2	(2)	2			(11)
Net unrealized gains on cash flow hedge derivatives	(17)	(2)	(22)			(9)
Total Other Comprehensive Activity
Other comprehensive income (loss)	(17)	(2)	(22)			(9)
Total Accumulated Other Comprehensive Income
Total Accumulated Other Comprehensive Income - Beginning Balance	(16)	3	(11)	[1]		10
Other comprehensive income (loss), Net of Tax	(17)	(2)	(22)			(9)
Total Accumulated Other Comprehensive Income - Ending Balance	(33)	1	(33)		(33)	1
Amortization Of Defined Benefit Pension Items
Pre-tax activity for defined benefit plans, net
Net actuarial loss	(2)	(3)	(2)			(4)
Reclassification of amounts to net periodic benefit costs	3	5	7			9
Defined benefit plans, net	1	2	5			5
Tax effect for defined benefit plans, net
Net actuarial loss	0	1	0			1
Reclassification of amounts to net periodic benefit costs	0	(2)	(2)			(3)
Defined benefit plans, net	0	(1)	(2)			(2)
Net activity for defined benefit plans, net
Net actuarial gain (loss) arising during the period	(2)	(2)	(2)			(3)
Reclassification of amounts to net periodic benefit costs	3	3	5			6
Defined benefit plans, net	1	1	3			3
Total Other Comprehensive Activity
Other comprehensive income (loss)	(1)	(1)	3			3
Total Accumulated Other Comprehensive Income
Total Accumulated Other Comprehensive Income - Beginning Balance	(51)	(50)	(53)	[1]		(52)
Other comprehensive income (loss), Net of Tax	(1)	(1)	3			3
Total Accumulated Other Comprehensive Income - Ending Balance	$ (50)	$ (49)	$ (50)		$ (50)	$ (49)

[1] The Bancorp’s AOCI balance was adjusted as of January 1, 2018 to reflect the adoption of new accounting standards. Refer to Note 3 for additional information.