Long-Term Debt (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Debt Instrument [Line Items]
Long-term Debt	$ 1,187,300,000		$ 1,187,300,000		$ 1,176,700,000
Long-term Debt, Current Maturities	98,000		98,000		95,000
Notes payable, long term	1,187,238,000		1,187,238,000		1,176,622,000
Interest expense before capitalization of interest	(27,000,000)	(27,400,000)	(54,000,000)	(51,900,000)
Less: capitalized interest	1,300,000	0	2,211,000	3,500,000
Interest expense, net of capitalized interest	25,651,000	27,417,000	51,841,000	48,369,000
Line of Credit Facility, Maximum Borrowing Capacity	375,000,000		375,000,000
Loss on early extinguishment of debt	0	434,000	0	1,852,000
Long-term Debt, Fair Value	1,300,000,000		1,300,000,000		1,300,000,000
Letter of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	9,800,000		9,800,000
Senior Secured Credit Facility [Member]
Debt Instrument [Line Items]
Long-term Debt	10,000,000		10,000,000		0
Senior Subordinated Notes Due 2020 [Member]
Debt Instrument [Line Items]
Long-term Debt	350,000,000		350,000,000		350,000,000
Debt Instrument, Interest Rate, Stated Percentage	8.75%		8.75%
Senior Notes Due 2017 [Member]
Debt Instrument [Line Items]
Long-term Debt	444,800,000		444,800,000		444,500,000
Debt Instrument, Interest Rate, Stated Percentage	8.625%		8.625%
Senior Subordinated Notes due 2015 [Member]
Debt Instrument [Line Items]
Long-term Debt	381,800,000		381,800,000		381,500,000
Debt Instrument, Interest Rate, Stated Percentage	7.50%		7.50%
Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 700,000		$ 700,000		$ 700,000