Investment Securities (Gains And Losses On Available-For-Sale Securities) (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Securities gains										$ 0	$ 0	$ 2
Securities losses	[1]									(5)	(2)	(2)
Net securities losses		$ (2)	$ 0	$ (1)	$ (2)	$ 0	$ 0	$ 0	$ (2)	$ (5)	$ (2)	$ 0

[1] Primarily charges related to a derivative contract tied to the conversion rate of Visa Class B shares.