Commitments (Commitments, Contingent Liabilities and Guarantees - Additional Information) (Detail) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 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	$ 2,185		$ 2,583
Margin account balance held by the brokerage clearing agent	15		15
Amount in excess of amounts reserved	31
Credit loss reserve	1,196	[1]	1,253	[1]	$ 1,272	$ 1,322
Visa Class B shares carryover basis													$ 0
Residential Mortgage
Loss Contingencies
Amount in excess of amounts reserved	11
Outstanding balances on residential mortgage loans sold with representation and warranty provisions	9		13		$ 25
Outstanding balances on residential mortgage loans sold with credit recourse	$ 312		$ 374
Delinquency Rates	3.00%		3.20%
Credit loss reserve	$ 5		$ 7
Make Whole Payments	1		1
Repurchased Outstanding Principal	12		17
Repurchase Demand Request	15		22
Outstanding Repurchase Demand Inventory	1		2
Secured Debt
Loss Contingencies
Fully and unconditionally guaranteed certain long-term borrowing obligations issued by wholly-owned issuing trust entities	62		62
Standby Letters of Credit
Loss Contingencies
Reserve for unfunded commitments	$ 6		$ 3
Standby letters of credit as a percentage of total letters of credit	99.00%		99.00%
Standby Letters of Credit | Secured Debt
Loss Contingencies
Standby letters of credit as a percentage of total letters of credit	61.00%		62.00%
Variable Rate Demand Note
Loss Contingencies
Fifth Third Securities, Inc. (FTS) acted as the remarketing agent to issuers of VRDNs	$ 508		$ 784
Letters of Credit	94		145
Total Variable Rate Demand Notes	602		929
Letters Credit Issued Related Variable Rate Demand Notes	331		609
Variable Rate Demand Note | Trading Securities
Loss Contingencies
Total Variable Rate Demand Notes	1		6
Other Liabilities
Loss Contingencies
Reserve for unfunded commitments	161
Other Liabilities | Residential Mortgage
Loss Contingencies
Outstanding balances on residential mortgage loans sold with representation and warranty provisions	9		13
Visa Litigation
Loss Contingencies
Recorded share of litigation formally settled by Visa and for probable future litigation settlements	$ 137		$ 91
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 $ 0 and $ 85 of cash and due from banks, $ 62 and $ 0 of other short-term investments, $ 1,297 and $ 1,216 of portfolio loans and leases, $ (6) and $ (26) of ALLL, $ 7 and $ 9 of other assets, $ 2 and $ 3 of other liabilities and $ 1,190 and $ 1,094 of long-term debt from consolidated VIEs that are included in their respective captions above at December 31, 2017 and 2016 , respectively. For further information, refer to Note 11 .