Long-Term Debt (Details) (USD $)	3 Months Ended		6 Months Ended								6 Months Ended			3 Months Ended			1 Months Ended				6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Jun. 30, 2013 Letter of Credit [Member]	Jun. 30, 2013 Term Loan	Dec. 31, 2012 Term Loan	Jun. 30, 2013 Credit Facility	Dec. 31, 2012 Credit Facility	Jun. 30, 2010 Senior Subordinated Notes Due 2020	Jun. 30, 2013 Senior Subordinated Notes Due 2020	Dec. 31, 2012 Senior Subordinated Notes Due 2020	Mar. 31, 2012 Senior Subordinated Notes Due 2022	Jun. 30, 2013 Senior Subordinated Notes Due 2022	Dec. 31, 2012 Senior Subordinated Notes Due 2022	Aug. 31, 2009 Senior Subordianted Notes Due 2017 [Member]	Jun. 30, 2013 Senior Notes Due 2017 [Member]	Dec. 31, 2012 Senior Notes Due 2017 [Member]	Aug. 31, 2009 Senior Notes Due 2017 [Member]	Jun. 30, 2012 Senior Subordinated Notes due 2015 [Member]	Jun. 30, 2013 LIBOR Term Loan	Jun. 30, 2013 Base Rate Term Loan	Jun. 30, 2013 Minimum LIBOR Term Loan
Debt Instrument [Line Items]
Long-term Debt	$ 1,459,500,000		$ 1,459,500,000		$ 1,440,500,000		$ 318,300,000	$ 319,700,000	$ 20,000,000	$ 0		$ 350,000,000	$ 350,000,000		$ 325,000,000	$ 325,000,000		$ 446,200,000	$ 445,800,000
Long-term Debt, Current Maturities	(3,250,000)		(3,250,000)		(3,250,000)		(3,250,000)
Long-term debt less current portion	1,456,232,000		1,456,232,000		1,437,251,000
Credit Facility, Maximum Borrowing Capacity									410,000,000
Letter of Credit, amount outstanding						8,100,000
Debt Instrument, Face Amount							325,000,000					350,000,000			325,000,000			450,000,000
Debt Instrument, Basis Spread on Variable Rate																						3.00%	1.50%	1.00%
Long-term Debt Instrument, Issuance Price, Percent of Face Amount																				98.597%
Debt Instrument, Interest Rate, Stated Percentage												8.75%			7.75%			8.625%
Loss on early extinguishment of debt	0	0	0	(20,718,000)																	20,700,000
Proceeds from issuance of debt											341,500,000			318,000,000			434,000,000
Interest expense	29,300,000	29,100,000	58,500,000	56,500,000
Interest income	(100,000)	(200,000)	(200,000)	(300,000)
Capitalized interest	(800,000)	(6,400,000)	(1,200,000)	(11,800,000)
Interest expense, net	$ 28,401,000	$ 22,485,000	$ 57,071,000	$ 44,403,000