Debt, Accounts Receivable Sales Facility and Capitalized Interest (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Capitalized Interest (Textual)
Interest costs incurred, capitalized	$ 16,000,000	$ 17,000,000
Credit Facilities [Member] | A/R Sales Facility [Member]
Accounts Receivable Sales Facility (Textual)
Line of credit facility, maximum borrowing capacity	1,500,000,000
Maturity date of accounts receivable sales facility	Jul. 31, 2015
Proceeds from accounts receivable sales facility	0	0
Repayments under accounts receivable sales facility	0	0
Amount outstanding	$ 100,000,000		$ 100,000,000