Commitments (Commitments, Contingent Liabilities and Guarantees - Additional Information) (Detail) - USD ($) shares in Millions, $ in Millions	3 Months Ended				9 Months Ended			12 Months Ended
	Sep. 30, 2016		Jun. 30, 2016	Sep. 30, 2015	Sep. 30, 2016		Sep. 30, 2015	Dec. 31, 2015		Dec. 31, 2013	Jun. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Sep. 30, 2012	Mar. 31, 2012	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010	Dec. 31, 2009
Loss Contingencies
Letters of credit	$ 2,606				$ 2,606			$ 3,055
Margin account balance held by the brokerage clearing agent	15				15			10
Amount in excess of amounts reserved	41				41
Credit loss reserve	1,272	[1],[2]	$ 1,299	$ 1,261	1,272	[1],[2]	$ 1,261	1,272	[1],[3]		$ 1,293	$ 1,322
Residential Mortgage
Loss Contingencies
Repurchase Claim Settlement										$ 25
Amount in excess of amounts reserved	11				11
Outstanding balances on residential mortgage loans sold with representation and warranty provisions	18		21	28	18		28	25			$ 32	$ 35
Outstanding balances on residential mortgage loans sold with credit recourse	$ 396				$ 396			$ 465
Delinquency Rates	3.00%				3.00%			3.00%
Credit loss reserve	$ 7				$ 7			$ 9
Make Whole Payments							2
Repurchased Outstanding Principal	4			7	10		64
Repurchase Demand Request	8			$ 7	18		$ 68
Outstanding Repurchase Demand Inventory	7							4
Secured Debt
Loss Contingencies
Fully and unconditionally guaranteed certain long-term borrowing obligations issued by wholly-owned issuing trust entities	62				62			$ 62
Standby Letters of Credit
Loss Contingencies
Reserve for unfunded commitments	$ 3				$ 3
Standby letters of credit as a percentage of total letters of credit	99.00%				99.00%			99.00%
Standby Letters of Credit | Secured Debt
Loss Contingencies
Standby letters of credit as a percentage of total letters of credit	63.00%				63.00%			65.00%
Variable Rate Demand Note
Loss Contingencies
Fifth Third Securities, Inc. (FTS) acted as the remarketing agent to issuers of VRDNs	$ 820				$ 820			$ 1,100
Letters of credit	154				154			187
Total Variable Rate Demand Notes	973				973			1,300
Letters of credit issued by the Bancorp related to variable rate demand notes	649				649			921
Other Liabilities
Loss Contingencies
Reserve for unfunded commitments	162				162			138
Other Liabilities | Residential Mortgage
Loss Contingencies
Outstanding balances on residential mortgage loans sold with representation and warranty provisions	18				18			25
Private Mortgage Reinsurance
Loss Contingencies
Total outstanding reinsurance coverage	$ 1				$ 1			27
Approximate reserve related to exposures within the reinsurance portfolio								2
Carrying value of collateral released to insurer due to terminated reinsurance agreement			6
Payment received related to the difference between the release of assets and the reserve liability assumed			$ 4
Private Mortgage Reinsurance | Lower Limit
Loss Contingencies
Reinsurance coverage ranges of the total PMI coverage	5.00%				5.00%
Private Mortgage Reinsurance | Upper Limit
Loss Contingencies
Reinsurance coverage ranges of the total PMI coverage	10.00%				10.00%
Visa Litigation
Loss Contingencies
Recorded share of litigation formally settled by Visa and for probable future litigation settlements	$ 103				$ 103			$ 61
Escrow Deposit																			$ 3,000
Visa
Loss Contingencies
Visa IPO, shares of Visa's Class B common stock received																			10.1
Escrow Deposit													$ 450	$ 150	$ 1,565	$ 400	$ 800	$ 500

[1] Includes $ 112 and $ 152 of cash and due from banks, $ 1,560 and $ 2,537 of portfolio loans and leases , $ (28) and $ (28) of ALLL, $ 11 and $ 14 of other assets, $ 3 and $ 3 of other liabilities , and $ 1,422 and $ 2,487 of long-term debt from consolidated VIEs that are included in their respective captions above at September 30, 2016 and December 31, 2015 , respectively. For further information refer to Note 10 .

[2] Includes $ 2 related to leveraged leases at September 30, 2016 .

[3] Includes $ 5 related to leveraged leases at December 31, 2015 .