Realized Gains and Losses Recognized in Income from Available-for-Sale Securities (Parenthetical) (Detail) (Interest-Only-Strip [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2014	Mar. 31, 2013
Interest-Only-Strip [Member]
Investment Holdings [Line Items]
Net gains on interest-only mortgage-backed securities	$ 1	$ 24

Net realized and unrealized gains on interest-only mortgage-backed securities

No definition available.

Name:	fitb_NetRealizedUnrealizedGainsIOStrips
Namespace Prefix:	fitb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration