Investment Securities (Summary Of Agency Securities Estimated Weighted Average Life Classifications) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Agency securities classified as available for sale, Fair value	$ 77,143	$ 100,442
Agency securities classified as available for sale, Amortized cost	$ 73,828	$ 98,670
Weighted Average Coupon	3.71%	3.68%
Weighted Average Yield	2.64%	3.07%
Less Than or Equal to Three Years [Member]
Fair Value	$ 2,713	$ 2,671
Amortized Cost	$ 2,686	$ 2,654
Weighted Average Coupon	3.48%	3.54%
Weighted Average Yield	1.88%	2.61%
Greater Than Three Years and Less Than or Equal to Five Years [Member]
Fair Value	$ 43,494	$ 10,822
Amortized Cost	$ 41,853	$ 10,563
Weighted Average Coupon	3.70%	3.85%
Weighted Average Yield	2.53%	3.20%
Greater Than Five Years [Member]
Fair Value	$ 30,864	$ 86,492
Amortized Cost	$ 29,210	$ 85,002
Weighted Average Coupon	3.73%	3.67%
Weighted Average Yield	2.88%	3.07%
Greater Than Ten Years [Member]
Fair Value	$ 72	$ 457
Amortized Cost	$ 79	$ 451
Weighted Average Coupon	4.33%	3.31%
Weighted Average Yield	3.39%	3.06%