Investment Securities (Details 2) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 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	6	241
Number of securities, 12 months or more	17	11
Number of securities, total	23	252
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Estimated Fair Value, Less than 12 months	$ 127	$ 1,759
Estimated Fair Value, 12 months or more	104	123
Estimated Fair Value, Total	231	1,882
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Gross Unrealized Losses, Less than 12 months	(1)	(67)
Gross Unrealized Losses, 12 months or more	(4)	(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	6	228
Number of securities, 12 months or more	17	6
Number of securities, total	23	234
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Estimated Fair Value, Less than 12 months	127	1,665
Estimated Fair Value, 12 months or more	104	24
Estimated Fair Value, Total	231	1,689
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Gross Unrealized Losses, Less than 12 months	(1)	(53)
Gross Unrealized Losses, 12 months or more	(4)	(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		13
Number of securities, 12 months or more		5
Number of securities, total		18
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Estimated Fair Value, Less than 12 months		94
Estimated Fair Value, 12 months or more		99
Estimated Fair Value, Total		193
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Gross Unrealized Losses, Less than 12 months		(14)
Gross Unrealized Losses, 12 months or more		(15)
Gross Unrealized Losses, Total		$ (29)