Investment Securities (Summary Of Agency Securities Estimated Weighted Average Life Classifications) (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Agency securities classified as available for sale, Fair value	$ 46,993	$ 52,120
Agency securities classified as available for sale, Amortized cost	$ 45,982	$ 52,147
Weighted Average Coupon	3.54%	3.54%
Weighted Average Yield	2.64%	2.75%
Greater Than One Year and Less Than or Equal to Three Years [Member]
Fair Value	$ 1,493	$ 167
Amortized Cost	$ 1,467	$ 163
Weighted Average Coupon	3.92%	4.02%
Weighted Average Yield	2.48%	2.66%
Greater Than Three Years and Less Than or Equal to Five Years [Member]
Fair Value	$ 15,984	$ 17,497
Amortized Cost	$ 15,556	$ 17,343
Weighted Average Coupon	3.30%	3.27%
Weighted Average Yield	2.44%	2.40%
Greater Than Five Years [Member]
Fair Value	$ 29,490	$ 34,206
Amortized Cost	$ 28,936	$ 34,391
Weighted Average Coupon	3.65%	3.67%
Weighted Average Yield	2.76%	2.93%
Greater Than Ten Years [Member]
Fair Value	$ 26	$ 250
Amortized Cost	$ 23	$ 250
Weighted Average Coupon	4.67%	3.56%
Weighted Average Yield	3.86%	3.08%