Other Assets (Other Assets - Additional Information) (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016		Dec. 31, 2015	Jun. 30, 2014	[1]	Sep. 30, 2013	[1]	Jun. 30, 2013	[1]	Dec. 31, 2012	[1]	Mar. 31, 2012	Jun. 30, 2009
Other assets
Percentage of Vantiv Holding, LLC sold to Advent for cash and warrants															51.00%
Vantiv Holding, LLC
Other assets
Percentage of Vantiv Holding, LLC sold to Advent for cash and warrants															51.00%
Percentage of ownership under the equity method of accounting	8.60%	8.60%	18.30%	[1]	18.30%	22.80%		25.10%		27.70%		33.10%		39.00%	49.00%
Payment From Vantiv Inc to Bancorp To Terminate And Settle Certain Remaining TRA Cash Flows			$ 171
Potential Termination And Settlement Of Tra Cash Flows			$ 394

[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.