Investment Securities (Summary Of Continuous Unrealized Loss Positions Of Available-For-Sale Security) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Document Period End Date	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Member]
Unrealized Loss Position For - Estimated Fair Value - Less than 12 Months	$ 4,783	$ 3,582
Unrealized Loss Position For - Unrealized Loss - Less than 12 Months	(72)	(15)
Unrealized Loss Position For - Estimated Fair Value - 12 Months or More	18,231	20,577
Unrealized Loss Position For - Unrealized Loss - 12 Months or More	(878)	(451)
Unrealized Loss Position For - Estimated Fair Value - Total	23,014	24,159
Unrealized Loss Position For - Unrealized Loss - Total	$ (950)	$ (466)