Investment Securities (Details 2) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2015 USD ($) securities	Dec. 31, 2014 USD ($) securities
Available For Sale Securities Continuous Unrealized Loss Position Qualitative Disclosure [Abstract]
Number of securities, less than 12 months | securities	20	0
Number of securities, 12 months or more | securities	11	15
Number of securities, total | securities	31	15
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Estimated Fair Value, Less than 12 months	$ 87	$ 0
Estimated Fair Value, 12 months or more	73	105
Estimated Fair Value, Total	160	105
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Gross Unrealized Losses, Less than 12 months	1	0
Gross Unrealized Losses, 12 months or more	3	3
Gross Unrealized Losses, Total	$ 4	$ 3
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 | securities	20	0
Number of securities, 12 months or more | securities	11	15
Number of securities, total | securities	31	15
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Estimated Fair Value, Less than 12 months	$ 87	$ 0
Estimated Fair Value, 12 months or more	73	105
Estimated Fair Value, Total	160	105
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Gross Unrealized Losses, Less than 12 months	1	0
Gross Unrealized Losses, 12 months or more	3	3
Gross Unrealized Losses, Total	$ 4	$ 3