Available-For-Sale Securities (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Investments, Debt and Equity Securities [Abstract]
Due in one year or less, Cost Basis	$ 155
Due after one year through five years, Cost Basis	614
Due after five through ten years, Cost Basis	33
Due after ten years, Cost Basis	30
Due in one year or less, Fair Value	156
Due after one year through five years, Fair Value	635
Due after five years through ten years, Fair Value	35
Due after ten years, Fair Value	30
Cost Basis	1,245
Fair Value	1,276
Schedule of Available-for-sale Securities
Cost Basis	1,433		1,438
Available-for-sale securities, Fair Value	1,562		1,570
Available-for-sale Securities, Proceeds, Gains and Losses
Proceeds from the sale of available-for-sale securities	115	98
Gross gains from the sale of available-for-sale securities	14	1
Gross losses from the sale of available-for-sale securities	0	0
U.S. governmental agency mortgage-backed securities
Schedule of Available-for-sale Securities
Cost Basis	326		322
Available-for-sale securities, Fair Value	326		321
Residential
Schedule of Available-for-sale Securities
Cost Basis	17		18
Available-for-sale securities, Fair Value	18		18
Commercial
Schedule of Available-for-sale Securities
Cost Basis	70		87
Available-for-sale securities, Fair Value	$ 76		$ 93