Fair Value Measurements (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Interest and marketable securities income	$ 24	$ 47	$ 34
Standard & Poor's, A Rating [Member] | Corporate and Asset-Backed Debt Securities
Percentage Of Company's Investments With Credit Quality Rating Less Than Single A And A2	1.00%
Fitch, A Rating [Member] | Corporate and Asset-Backed Debt Securities
Percentage Of Company's Investments With Credit Quality Rating Less Than Single A And A2	1.00%
Moody's, A2 Rating [Member] | Corporate and Asset-Backed Debt Securities
Percentage Of Company's Investments With Credit Quality Rating Less Than Single A And A2	1.00%