Investment Securities (Summary Of Continuous Unrealized Loss Positions Of Available-For-Sale Security) (Details) - Accumulated Other Comprehensive Income (Loss) [Member] - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Unrealized Loss Position For - Estimated Fair Value - Less than 12 Months	$ 730	$ 24,035
Unrealized Loss Position For - Unrealized Loss - Less than 12 Months	(1)	(200)
Unrealized Loss Position For - Estimated Fair Value - 12 Months or More	2,072	6,793
Unrealized Loss Position For - Unrealized Loss - 12 Months or More	(9)	(195)
Unrealized Loss Position For - Estimated Fair Value - Total	2,802	30,828
Unrealized Loss Position For - Unrealized Loss - Total	$ (10)	$ (395)