Common, Preferred and Treasury Stock (Common, Preferred, and Treasury Stock - Additional Information) (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2016
4.90% fixed-to-floating non-cumulative Series J perpetual preferred stock
Depositary shares		300,000
Preferred stock, issued	12,000	12,000		12,000
Issuance of preferred stock		$ 297
Preferred stock, liquidation preference	$ 25,000	$ 25,000		$ 25,000
Preferred Stock, Dividend Payment Terms	The preferred stock accrues dividends, on a non-cumulative semi-annual basis, at an annual rate of 4.90% through but excluding September 30, 2019, at which time it converts to a quarterly floating-rate dividend of three-month LIBOR plus 3.129%.
Preferred Stock, Redemption Terms	Subject to any required regulatory approval, the Bancorp may redeem the Series J preferred shares at its option, in whole or in part, at any time on or after September 30, 2019, or any time prior following a regulatory capital event
Preferred stock, shares authorized	12,000			12,000
Series I Preferred Stock
Depositary shares			18,000,000
Preferred stock, issued	18,000		18,000	18,000
Issuance of preferred stock			$ 441
Preferred stock, liquidation preference	$ 25,000		$ 25,000	$ 25,000
Preferred Stock, Dividend Payment Terms	The preferred stock accrues dividends, on a non-cumulative quarterly basis, at an annual rate of 6.625% through but excluding December 31, 2023, at which time it converts to a quarterly floating-rate dividend of three-month LIBOR plus 3.71%
Preferred Stock, Redemption Terms	Subject to any required regulatory approval, the Bancorp may redeem the Series I preferred shares at its option in whole or in part, at any time on or after December 31, 2023 and may redeem in whole but not in part, following a regulatory capital event at any time prior to December 31, 2023
Preferred stock, shares authorized	18,000			18,000
Preferred stock Series H
Depositary shares			600,000
Preferred stock, issued	24,000		24,000	24,000
Issuance of preferred stock			$ 593
Preferred stock, liquidation preference	$ 25,000		$ 25,000	$ 25,000
Preferred Stock, Dividend Payment Terms	The preferred stock accrues dividends, on a non-cumulative semi-annual basis, at an annual rate of 5.10% through but excluding June 30, 2023, at which time it converts to a quarterly floating-rate dividend of three-month LIBOR plus 3.033%
Preferred Stock, Redemption Terms	Subject to any required regulatory approval, the Bancorp may redeem the Series H preferred shares at its option in whole or in part, at any time on or after June 30, 2023 and may redeem in whole but not in part, following a regulatory capital event at any time prior to June 30, 2023
Preferred stock, shares authorized	24,000			24,000
March 2014 Repurchase Program
Stock Repurchase Authorization Amount				$ 765
March 2016 Repurchase Program
Stock Repurchase Authorization Amount				$ 660
Repurchase Shares Authorized				100