Fair Value Measurements (Unrealized Losses And Fair Value Of Investments With Unrealized Losses) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
Less Than 12 Months - Number of Investments	505
Less Than 12 Months - Fair Value	$ 1,609
Less Than 12 Months - Unrealized Losses	(2)
Total - Number of Investments	505
Total - Fair Value	1,609
Total - Unrealized Losses	(2)
Corporate and asset-backed debt securities
Less Than 12 Months - Number of Investments	333
Less Than 12 Months - Fair Value	722
Less Than 12 Months - Unrealized Losses	(1)
Total - Number of Investments	333
Total - Fair Value	722
Total - Unrealized Losses	(1)
Foreign government debt securities
Less Than 12 Months - Number of Investments	104
Less Than 12 Months - Fair Value	593
Less Than 12 Months - Unrealized Losses	(1)
Total - Number of Investments	104
Total - Fair Value	593
Total - Unrealized Losses	(1)
United States agency debt securities
Less Than 12 Months - Number of Investments	54
Less Than 12 Months - Fair Value	277
Total - Number of Investments	54
Total - Fair Value	277
Other
Less Than 12 Months - Number of Investments	14
Less Than 12 Months - Fair Value	17
Total - Number of Investments	14
Total - Fair Value	$ 17