Investment Securities (Details 2) (USD $) In Millions, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2014 securities	Dec. 31, 2013 securities
Available For Sale Securities Continuous Unrealized Loss Position Qualitative Disclosure [Abstract]
Number of securities, less than 12 months	0	241
Number of securities, 12 months or more	19	11
Number of securities, total	19	252
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Estimated Fair Value, Less than 12 months	$ 0	$ 1,759
Estimated Fair Value, 12 months or more	116	123
Estimated Fair Value, Total	116	1,882
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Gross Unrealized Losses, Less than 12 months	0	(67)
Gross Unrealized Losses, 12 months or more	(5)	(17)
Gross Unrealized Losses, Total	(5)	(84)
Ratio Of Fair Value To Amortized Cost Between Ninety And One Hundred Percent [Member]
Available For Sale Securities Continuous Unrealized Loss Position Qualitative Disclosure [Abstract]
Number of securities, less than 12 months	0	228
Number of securities, 12 months or more	19	6
Number of securities, total	19	234
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Estimated Fair Value, Less than 12 months	0	1,665
Estimated Fair Value, 12 months or more	116	24
Estimated Fair Value, Total	116	1,689
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Gross Unrealized Losses, Less than 12 months	0	(53)
Gross Unrealized Losses, 12 months or more	(5)	(2)
Gross Unrealized Losses, Total	(5)	(55)
Ratio Of Fair Value To Amortized Cost Less Than Ninety Percent [Member]
Available For Sale Securities Continuous Unrealized Loss Position Qualitative Disclosure [Abstract]
Number of securities, less than 12 months	0	13
Number of securities, 12 months or more	0	5
Number of securities, total	0	18
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Estimated Fair Value, Less than 12 months	0	94
Estimated Fair Value, 12 months or more	0	99
Estimated Fair Value, Total	0	193
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Gross Unrealized Losses, Less than 12 months	0	(14)
Gross Unrealized Losses, 12 months or more	0	(15)
Gross Unrealized Losses, Total	$ 0	$ (29)