Securities Available for Sale and Securities Held to Maturity (Available For Sale Securities with Unrealized Losses, Aggregated by Category and Period of Continuous Unrealized Loss) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014 security	Dec. 31, 2013 security
Schedule Of Available For Sale Securities [Line Items]
Securities available for sale Less than 12 months Fair Value	$ 14,204	$ 16,962
Securities available for sale Less than 12 months Unrealized Losses	132	200
Securities available for sale 12 months or longer Fair Value	1,795	1,856
Securities available for sale 12 months or longer Unrealized Losses	34	41
Total Securities available for sale with unrealized losses Total Fair Value	15,999	18,818
Total Securities available for sale with unrealized losses Total Unrealized Losses	166	241
Number of available for sale securities in unrealized loss positions	264	273
U.S. agency mortgage-backed securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Securities available for sale Less than 12 months Fair Value	6,119	5,044
Securities available for sale Less than 12 months Unrealized Losses	37	47
Securities available for sale 12 months or longer Fair Value	176	93
Securities available for sale 12 months or longer Unrealized Losses	1	2
Total Securities available for sale with unrealized losses Total Fair Value	6,295	5,137
Total Securities available for sale with unrealized losses Total Unrealized Losses	38	49
Asset-backed securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Securities available for sale Less than 12 months Fair Value	1,887	6,391
Securities available for sale Less than 12 months Unrealized Losses	5	33
Securities available for sale 12 months or longer Fair Value	769	591
Securities available for sale 12 months or longer Unrealized Losses	3	4
Total Securities available for sale with unrealized losses Total Fair Value	2,656	6,982
Total Securities available for sale with unrealized losses Total Unrealized Losses	8	37
Corporate debt securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Securities available for sale Less than 12 months Fair Value	1,180	1,802
Securities available for sale Less than 12 months Unrealized Losses	8	14
Securities available for sale 12 months or longer Fair Value	400	499
Securities available for sale 12 months or longer Unrealized Losses	1	1
Total Securities available for sale with unrealized losses Total Fair Value	1,580	2,301
Total Securities available for sale with unrealized losses Total Unrealized Losses	9	15
U.S. agency notes [Member]
Schedule Of Available For Sale Securities [Line Items]
Securities available for sale Less than 12 months Fair Value	3,909	3,636
Securities available for sale Less than 12 months Unrealized Losses	81	104
Total Securities available for sale with unrealized losses Total Fair Value	3,909	3,636
Total Securities available for sale with unrealized losses Total Unrealized Losses	81	104
Certificates of deposit [Member]
Schedule Of Available For Sale Securities [Line Items]
Securities available for sale Less than 12 months Fair Value	1,050
Securities available for sale 12 months or longer Fair Value	98	299
Securities available for sale 12 months or longer Unrealized Losses	2	2
Total Securities available for sale with unrealized losses Total Fair Value	1,148	299
Total Securities available for sale with unrealized losses Total Unrealized Losses	2	2
Non-agency residential mortgage-backed securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Securities available for sale Less than 12 months Fair Value	59	89
Securities available for sale Less than 12 months Unrealized Losses	1	2
Securities available for sale 12 months or longer Fair Value	352	374
Securities available for sale 12 months or longer Unrealized Losses	27	32
Total Securities available for sale with unrealized losses Total Fair Value	411	463
Total Securities available for sale with unrealized losses Total Unrealized Losses	$ 28	$ 34