Debt 7.75% Senior Subordinated Notes (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Long-term Debt, Gross	$ 2,473,927,000	$ 2,381,929,000
Current Fiscal Year End Date	--12-31
Derivative, Fair Value, Net		35,473,000
7.75% Senior Subordinated Notes, Due 2020 [Member]
Long-term Debt, Gross	550,000,000	550,000,000
Debt Instrument, Interest Rate, Stated Percentage	7.75%
Debt Instrument, Initial Face Value	400,000,000
Deferred Finance Costs, Gross	12,600,000
Amortization of Financing Costs	1,200,000	1,100,000	600,000
Offering Of Additional Senior Subordinated Notes Aggregate Principal Amount	$ 150,000,000
Derivative, Variable Interest Rate	4.77%
Initial 7.75% Swap Agreement [Member] | 7.75% Senior Subordinated Notes, Due 2020 [Member]
Derivative, Basis Spread on Variable Rate	3.87%
Additional 7.75% swap agreement [Member] | 7.75% Senior Subordinated Notes, Due 2020 [Member]
Derivative, Basis Spread on Variable Rate	5.32%