Short-Term And Long-Term Investments And Restricted Deposits (Contractual Maturities Of Short-Term And Long-Term Investments And Restricted Deposits) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
One year or less, Amortized Cost	$ 176	$ 102
One year through five years, Amortized Cost	1,121	610
Five years through ten years, Amortized Cost	121	157
Greater than ten years, Amortized Cost	38	30
Total, Amortized Cost	1,456	899
One year or less, Fair Value	177	102
One year through five years, Fair Value	1,121	611
Five years through ten years, Fair Value	120	151
Greater than ten years, Fair Value	39	30
Total, Fair Value	1,457	894
Restricted Deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
One year or less, Amortized Cost	92	41
One year through five years, Amortized Cost	8	6
Five years through ten years, Amortized Cost	0	0
Greater than ten years, Amortized Cost	0	0
Total, Amortized Cost	100	47
One year or less, Fair Value	92	41
One year through five years, Fair Value	8	6
Five years through ten years, Fair Value	0	0
Greater than ten years, Fair Value	0	0
Total, Fair Value	$ 100	$ 47

Short-Term And Long-Term Investments And Restricted Deposits (Contractual Maturities Of Short-Term And Long-Term Investments And Restricted Deposits) (Details) (USD $)
In Millions, unless otherwise specified

Dec. 31, 2014

Dec. 31, 2013

Schedule of Available-for-sale Securities [Line Items]

One year or less, Amortized Cost

$ 176

$ 102

One year through five years, Amortized Cost

1,121

610

Five years through ten years, Amortized Cost

121

157