Available-For-Sale Securities (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Due in one year or less, Cost Basis	$ 58
Due after one year through five years, Cost Basis	723
Due after five through ten years, Cost Basis	39
Due after ten years, Cost Basis	30
Due in one year or less, Fair Value	58
Due after one year through five years, Fair Value	743
Due after five years through ten years, Fair Value	41
Due after ten years, Fair Value	31
Cost Basis	1,201
Fair Value	1,232
Schedule of Available-for-sale Securities
Cost Basis	1,393		1,421
Available-for-sale securities, Fair Value	1,535		1,554
Available-for-sale Securities, Proceeds, Gains and Losses
Proceeds from the sale of available-for-sale securities	83	115
Gross gains from the sale of available-for-sale securities	5	14
Gross losses from the sale of available-for-sale securities	1	0
U.S. governmental agency mortgage-backed securities
Schedule of Available-for-sale Securities
Cost Basis	277		292
Available-for-sale securities, Fair Value	281		294
Residential
Schedule of Available-for-sale Securities
Cost Basis	14		15
Available-for-sale securities, Fair Value	14		15
Commercial
Schedule of Available-for-sale Securities
Cost Basis	60		63
Available-for-sale securities, Fair Value	$ 64		$ 67