Disclosure of Fair Value of Financial Instruments Disclosure of Fair Value of Financial Instruments - Level 3 Rollforward (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2012		Dec. 31, 2011
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Calculation, Input, Discount Rate	3.09%		3.87%
Long-tern Debt [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value of long-term debt at beginning of year	2,215,219	[1]
Payoffs and amortization of long-term debt	(258,203)	[1]
New long-term debt	427,481	[1]
Changes in fair value inputs	103,044	[1]
Fair value of long-term debt at end of period	2,487,541	[1]
Carrying Value of Debt to be Fair Valued [Roll Forward]
Long-term Debt at start of period	2,083,462	[1]
Repayments of Long-term Debt	(258,203)	[1]
Proceeds from Issuance of Long-term Debt	427,481	[1]
Long-term Debt at end of period	2,252,740	[1]
Fair Value Above (Below) Carrying Value [Roll Forward]
Fair Value of Debt, Greater than Aggregate Carrying Value at start of period	131,757	[1]
Changes in fair value inputs	103,044	[1]
Fair Value of Debt, Greater than Aggregate Carrying Value at end of period	234,801	[1]

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