Other Financial Information (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Other Current Assets
Prepaid expenses	$ 63	$ 45
Other	80	80
Total other current assets	143	125
Selected Current Liabilities
Accounts payable	478	464
Capital expenditures incurred but not paid	$ 28	$ 44