Debt, Accounts Receivable Sales Facility and Capitalized Interest (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Jun. 30, 2015	Dec. 31, 2014
Capitalized Interest (Textual)
Interest costs incurred, capitalized	$ 18,000,000	$ 17,000,000	$ 50,000,000	$ 52,000,000
Credit Facilities [Member] | A/R Sales Facility [Member]
Accounts Receivable Sales Facility (Textual)
Line of credit facility, maximum borrowing capacity	1,400,000,000		$ 1,400,000,000		$ 1,500,000,000
Maturity date of accounts receivable sales facility			Jul. 31, 2016
Amount outstanding	$ 100,000,000		$ 100,000,000			$ 100,000,000