Investment Securities (Components Of Investment Securities) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Amortized cost	$ 53,301	$ 67,025
Gross unrealized gains	654	276
Gross unrealized losses	(404)	(1,360)
Available-for-sale Securities, Fair Value Disclosure	53,127	65,504
Available-for-sale Securities, Amortized Cost Basis	52,904	66,593
Total agency MBS, at fair value	53,551	65,941
Total Agency Securities	53,551	65,941
Fixed-Rate [Member]
Gross unrealized gains	581	242
Gross unrealized losses	(401)	(1,338)
Available-for-sale Securities, Fair Value Disclosure	50,871	62,961
Adjustable-Rate [Member]
Gross unrealized gains	21	15
Gross unrealized losses	0	(3)
Available-for-sale Securities, Fair Value Disclosure	988	1,235
CMO [Member]
Gross unrealized gains	22	3
Gross unrealized losses	0	(8)
Available-for-sale Securities, Fair Value Disclosure	1,268	1,308
Agency Securities [Member] | Fixed-Rate [Member]
Available-for-sale Securities, Amortized Cost Basis	50,691	64,057
Agency Securities [Member] | Adjustable-Rate [Member]
Available-for-sale Securities, Amortized Cost Basis	967	1,223
Agency Securities [Member] | CMO [Member]
Available-for-sale Securities, Amortized Cost Basis	1,246	1,313
Agency Securities [Member] | Interest Only And Principal Only Strip [Member]
Amortized cost	397	432
Gross unrealized gains	30	16
Gross unrealized losses	(3)	(11)
Fair Value	$ 424	$ 437