Annual report pursuant to Section 13 and 15(d)

Supplemental Cash Flow Information (Details)

Supplemental Cash Flow Information (Details) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Supplemental Cash Flow Information [Abstract]      
Cash paid during the year for interest, net of amounts capitalized and deferred $ 130,578us-gaap_InterestPaidNet $ 120,908us-gaap_InterestPaidNet $ 200,323us-gaap_InterestPaidNet
Balance in property, plant and equipment, net funded with accounts payable and accrued liabilities $ 129,842us-gaap_ConstructionInProgressExpendituresIncurredButNotYetPaid $ 154,517us-gaap_ConstructionInProgressExpendituresIncurredButNotYetPaid $ 99,751us-gaap_ConstructionInProgressExpendituresIncurredButNotYetPaid