Credit Quality (Summarizes the Bancorp's Recorded Investment in Impaired Loans and Related Allowance by Class) (Parenthetical) (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Impaired
Unpaid Principal Balance	$ 1,492	$ 1,679
Commercial Portfolio Segment | TDR on accrual status
Financing Receivable, Impaired
Unpaid Principal Balance	80	249
Commercial Portfolio Segment | TDR on nonaccrual status
Financing Receivable, Impaired
Unpaid Principal Balance	180	150
Residential Mortgage Loans | TDR on accrual status
Financing Receivable, Impaired
Unpaid Principal Balance	745	652
Residential Mortgage Loans | TDR on nonaccrual status
Financing Receivable, Impaired
Unpaid Principal Balance	12	13
Consumer Portfolio Segment | TDR on accrual status
Financing Receivable, Impaired
Unpaid Principal Balance	242	275
Consumer Portfolio Segment | TDR on nonaccrual status
Financing Receivable, Impaired
Unpaid Principal Balance	$ 43	$ 45