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	Sep. 30, 2014 security	Dec. 31, 2013 security
Schedule Of Available For Sale Securities [Line Items]
Securities available for sale Less than 12 months Fair Value	$ 5,626	$ 16,962
Securities available for sale Less than 12 months Unrealized Losses	13	200
Securities available for sale 12 months or longer Fair Value	7,071	1,856
Securities available for sale 12 months or longer Unrealized Losses	105	41
Total Securities available for sale with unrealized losses Total Fair Value	12,697	18,818
Total Securities available for sale with unrealized losses Total Unrealized Losses	118	241
Number of available for sale securities in unrealized loss positions	209	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	2,414	5,044
Securities available for sale Less than 12 months Unrealized Losses	6	47
Securities available for sale 12 months or longer Fair Value	1,629	93
Securities available for sale 12 months or longer Unrealized Losses	9	2
Total Securities available for sale with unrealized losses Total Fair Value	4,043	5,137
Total Securities available for sale with unrealized losses Total Unrealized Losses	15	49
Asset-backed securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Securities available for sale Less than 12 months Fair Value	1,928	6,391
Securities available for sale Less than 12 months Unrealized Losses	4	33
Securities available for sale 12 months or longer Fair Value	841	591
Securities available for sale 12 months or longer Unrealized Losses	2	4
Total Securities available for sale with unrealized losses Total Fair Value	2,769	6,982
Total Securities available for sale with unrealized losses Total Unrealized Losses	6	37
Corporate debt securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Securities available for sale Less than 12 months Fair Value	1,010	1,802
Securities available for sale Less than 12 months Unrealized Losses	1	14
Securities available for sale 12 months or longer Fair Value	616	499
Securities available for sale 12 months or longer Unrealized Losses	5	1
Total Securities available for sale with unrealized losses Total Fair Value	1,626	2,301
Total Securities available for sale with unrealized losses Total Unrealized Losses	6	15
U.S. agency notes [Member]
Schedule Of Available For Sale Securities [Line Items]
Securities available for sale Less than 12 months Fair Value	249	3,636
Securities available for sale Less than 12 months Unrealized Losses	1	104
Securities available for sale 12 months or longer Fair Value	3,674
Securities available for sale 12 months or longer Unrealized Losses	66
Total Securities available for sale with unrealized losses Total Fair Value	3,923	3,636
Total Securities available for sale with unrealized losses Total Unrealized Losses	67	104
Certificates of deposit [Member]
Schedule Of Available For Sale Securities [Line Items]
Securities available for sale 12 months or longer Fair Value		299
Securities available for sale 12 months or longer Unrealized Losses		2
Total Securities available for sale with unrealized losses Total Fair Value		299
Total Securities available for sale with unrealized losses Total Unrealized Losses		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	25	89
Securities available for sale Less than 12 months Unrealized Losses	1	2
Securities available for sale 12 months or longer Fair Value	311	374
Securities available for sale 12 months or longer Unrealized Losses	23	32
Total Securities available for sale with unrealized losses Total Fair Value	336	463
Total Securities available for sale with unrealized losses Total Unrealized Losses	$ 24	$ 34