Long-Term Debt (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Long-term Debt
Long-term Debt	$ 1,440,500,000	$ 1,224,000,000
Current portion of long-term debt	3,250,000	111,000
Long-term debt less current portion	1,437,251,000	1,223,874,000
Interest Expense	114,800,000	106,000,000	107,100,000
Interest Income	800,000	400,000	200,000
Capitalized Interest	(20,300,000)	(10,300,000)	(4,000,000)
Total Interest expense, net of capitalized interest	93,687,000	95,308,000	102,867,000
Senior Secured Credit Facility
Long-term Debt
Long-term Debt	0	56,000,000
Term Loan
Long-term Debt
Long-term Debt	319,700,000	0
Current portion of long-term debt	3,250,000
7.75% Senior Subordinated Notes Due 2022
Long-term Debt
Long-term Debt	325,000,000	0
8.75% Senior Subordinated Notes due 2020
Long-term Debt
Long-term Debt	350,000,000	350,000,000
8.625% Senior Notes Due 2017
Long-term Debt
Long-term Debt	445,800,000	445,100,000
7.50% Senior Subordinated Notes due 2015
Long-term Debt
Long-term Debt	0	372,200,000
Other secured and unsecured notes payable
Long-term Debt
Long-term Debt	$ 0	$ 700,000