Related Party (Summary of Vantiv Holding, LLC Sales Transactions) (Detail) - USD ($) $ in Millions	3 Months Ended											12 Months Ended
	Sep. 30, 2017	Dec. 31, 2015	Jun. 30, 2014		Sep. 30, 2013		Jun. 30, 2013		Dec. 31, 2012		Mar. 31, 2012	Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015	Jun. 30, 2009
Related Party Transactions
Gain on sale of Vantiv, Inc. shares												$ 1,037	$ 0		$ 331
Vantiv Holding, LLC
Related Party Transactions
Gain on sale of Vantiv, Inc. shares	$ 1,037	$ 331	$ 125		$ 85		$ 242		$ 157		$ 115	$ 1,000
Equity Method Investment, Ownership Percentage	8.60%	18.30%	22.80%	[1]	25.10%	[1]	27.70%	[1]	33.10%	[1]	39.00%	8.60%	18.30%	[1]	18.30%	49.00%

[1] (a) The Bancorp’s remaining investment in Vantiv Holding, LLC of $ 219 as of December 31, 201 7 was accounted for as an equity method investment in the Bancorp’s Consolidated Financial Statements.