Parent Company Financial Statements (Condensed Statement of Cash Flow - Parent Company Only) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
Operating Activities
Net income (loss)		$ 2,193	$ 2,180		$ 1,547
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
(Benefit from) provision for deferred income taxes		30	(252)	[1]	(141)	[1]
Net change in undistributed earnings		1	47		66
Net change in:
Other assets		303	(22)	[1]	338	[1]
Accrued expenses and other liabilities		147	(138)	[1]	(157)	[1]
Net Cash Provided by (Used in) Operating Activities		2,856	1,480	[1]	2,091	[1]
Net change in:
Other short-term investments		928	1	[1]	(83)	[1]
Net Cash Provided by (Used in) Investing Activities		(4,141)	428	[1]	(2,864)	[1]
Financing Activities
Net change in other short-term borrowings		(3,439)	477	[1]	2,028	[1]
Dividends paid on common shares		467	430	[1]	402	[1]
Dividends paid on preferred shares		98	75	[1]	52	[1]
Proceeds from issuance of long-term debt		2,438	2,490	[1]	3,735	[1]
Repayment of long-term debt		2,884	1,969	[1]	5,119	[1]
Repurchase of treasury stock and related forward contract		1,453	1,605	[1]	661	[1]
Other, net		(69)	(57)	[1]	(31)	[1]
Net Cash Provided (Used in) Provided by Financing Activities		1,452	(1,786)	[1]	625	[1]
Net (Decrease) Increase in Cash		167	122	[1]	(148)	[1]
Cash and Due from Banks at Beginning of Period	[1]	2,514	2,392		2,540
Cash and Due from Banks at End of Period		2,681	2,514	[1]	2,392	[1]
Parent Company Only
Operating Activities
Net income (loss)		2,193	2,180		1,547
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
(Benefit from) provision for deferred income taxes		3	2		0
Net change in undistributed earnings		(474)	34		231
Net change in:
Other assets		61	37		14
Accrued expenses and other liabilities		(116)	(15)		(35)
Net Cash Provided by (Used in) Operating Activities		1,667	2,238		1,757
Net change in:
Other short-term investments		(149)	(419)		654
Loans to subsidiaries		272	126		13
Net Cash Provided by (Used in) Investing Activities		123	(293)		667
Financing Activities
Net change in other short-term borrowings		(62)	(29)		(60)
Dividends paid on common shares		(467)	(430)		(402)
Dividends paid on preferred shares		(98)	(75)		(52)
Proceeds from issuance of long-term debt		895	697		0
Repayment of long-term debt		(500)	(500)		(1,250)
Repurchase of treasury stock and related forward contract		(1,453)	(1,605)		(661)
Other, net		(65)	(53)		3
Net Cash Provided (Used in) Provided by Financing Activities		(1,750)	(1,995)		(2,422)
Net (Decrease) Increase in Cash		40	(50)		2
Cash and Due from Banks at Beginning of Period		80	130		128
Cash and Due from Banks at End of Period		$ 120	$ 80		$ 130

[1] Effective in the fourth quarter of 2018, Fifth Third retrospectively applied a change in its accounting policy for investments in affordable housing projects that qualify for LIHTC in accordance with ASU 2014-01. Refer to Note 1 for additional information.