Disclosure of Fair Value of Financial Instruments Disclosure of Fair Value of Financial Instruments - Level 3 Rollforward (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Calculation, Input, Discount Rate	3.92%
Long-tern Debt [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Long-term debt at December 31, 2011	2,215,219	[1]
Payoffs and amortization of long-term debt	(19,289)
New long-term debt	11,186
Changes in fair value inputs	20,377
Long-term debt at March 31, 2012	2,227,493	[1]
Carrying Value of Debt to be Fair Valued [Roll Forward]
Long-term Debt	2,083,462	[1]
Repayments of Long-term Debt	(19,289)
Proceeds from Issuance of Long-term Debt	11,186
Long-term Debt	2,075,359	[1]
Fair Value Above (Below) Carrying Value [Roll Forward]
Fair Value of Debt, Greater than Aggregate Carrying Value	131,757	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Period Increase (Decrease)	20,377
Fair Value of Debt, Greater than Aggregate Carrying Value	152,134	[1]

[1] Does not include the Company's credit facility.