Property, Plant and Equipment (Asset Retirement Obligations) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	$ 209,000,000	$ 142,000,000
Additional liabilities incurred	43,000,000	51,000,000
Asset Retirement Obligation, Other [Line Items]	(5,000,000)	0
Liabilities settled	(6,000,000)	(11,000,000)
Accretion expense	13,000,000	12,000,000
Change in estimated cash flows	(7,000,000)	15,000,000
Ending balance	247,000,000	209,000,000
Asset retirement obligation, legally restricted	$ 2,000,000	$ 0