Securities (Gross Unrealized Losses and Fair Values of Investments by Investment Category and Length of Time) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Fair value of temporarily impaired AFS securities, less than 12 months	$ 10,525	$ 2,714
Unrealized losses on temporarily impaired AFS securities, less than 12 months	415	19
Fair value of temporarily impaired AFS securities, 12 months or more	2,376	591
Unrealized losses on temporarily impaired AFS securities, 12 months or more	223	100
Total fair value of temporarily impaired AFS securities	12,901	3,305
Total unrealized losses on temporarily impaired AFS securities	638	119
Fair value of temporarily impaired HTM securities, less than 12 months	14,180	1,686
Unrealized losses on temporarily impaired HTM securities, less than 12 months	624	6
Fair value of temporarily impaired HTM securities, 12 months or more	48	0
Unrealized losses on temporarily impaired HTM securities, 12 months or more	1	0
Total fair value of temporarily impaired HTM securities	14,228	1,686
Total unrealized losses on temporarily impaired HTM securities	625	6
GSE Securities
Fair value of temporarily impaired HTM securities, less than 12 months	4,996	805
Unrealized losses on temporarily impaired HTM securities, less than 12 months	397	1
Fair value of temporarily impaired HTM securities, 12 months or more	0	0
Unrealized losses on temporarily impaired HTM securities, 12 months or more	0	0
Total fair value of temporarily impaired HTM securities	4,996	805
Total unrealized losses on temporarily impaired HTM securities	397	1
MBS Issued by GSE
Fair value of temporarily impaired AFS securities, less than 12 months	10,259	2,662
Unrealized losses on temporarily impaired AFS securities, less than 12 months	406	18
Fair value of temporarily impaired AFS securities, 12 months or more	1,935	0
Unrealized losses on temporarily impaired AFS securities, 12 months or more	140	0
Total fair value of temporarily impaired AFS securities	12,194	2,662
Total unrealized losses on temporarily impaired AFS securities	546	18
Fair value of temporarily impaired HTM securities, less than 12 months	8,800	593
Unrealized losses on temporarily impaired HTM securities, less than 12 months	219	1
Fair value of temporarily impaired HTM securities, 12 months or more	48	0
Unrealized losses on temporarily impaired HTM securities, 12 months or more	1	0
Total fair value of temporarily impaired HTM securities	8,848	593
Total unrealized losses on temporarily impaired HTM securities	220	1
States and Political Subdivisions [Member]
Fair value of temporarily impaired AFS securities, less than 12 months	232	52
Unrealized losses on temporarily impaired AFS securities, less than 12 months	8	1
Fair value of temporarily impaired AFS securities, 12 months or more	441	478
Unrealized losses on temporarily impaired AFS securities, 12 months or more	83	89
Total fair value of temporarily impaired AFS securities	673	530
Total unrealized losses on temporarily impaired AFS securities	91	90
Fair value of temporarily impaired HTM securities, less than 12 months		22
Unrealized losses on temporarily impaired HTM securities, less than 12 months		1
Fair value of temporarily impaired HTM securities, 12 months or more		0
Unrealized losses on temporarily impaired HTM securities, 12 months or more		0
Total fair value of temporarily impaired HTM securities		22
Total unrealized losses on temporarily impaired HTM securities		1
Non-Agency Mortgage-Backed Securities [Member]
Fair value of temporarily impaired AFS securities, less than 12 months		0
Unrealized losses on temporarily impaired AFS securities, less than 12 months		0
Fair value of temporarily impaired AFS securities, 12 months or more		113
Unrealized losses on temporarily impaired AFS securities, 12 months or more		11
Total fair value of temporarily impaired AFS securities		113
Total unrealized losses on temporarily impaired AFS securities		11
Other Securities [Member]
Fair value of temporarily impaired AFS securities, less than 12 months	34
Unrealized losses on temporarily impaired AFS securities, less than 12 months	1
Total fair value of temporarily impaired AFS securities	34
Total unrealized losses on temporarily impaired AFS securities	1
Fair value of temporarily impaired HTM securities, less than 12 months		266
Unrealized losses on temporarily impaired HTM securities, less than 12 months		3
Fair value of temporarily impaired HTM securities, 12 months or more		0
Unrealized losses on temporarily impaired HTM securities, 12 months or more		0
Total fair value of temporarily impaired HTM securities		266
Total unrealized losses on temporarily impaired HTM securities		$ 3