Disclosure of Fair Value of Financial Instruments Disclosure of Fair Value of Financial Instruments - Level 3 Rollforward (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended		12 Months Ended
	Jun. 30, 2013		Dec. 31, 2012
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Inputs, Discount Rate	3.63%		2.87%
Long-tern Debt [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Long-term debt at December 31, 2012 (1)	$ 2,841,917	[1]
Payoffs and amortization of long-term debt (1)	(2,115)	[1]
New long-term debt (1)	6,738	[1]
Changes in fair value assumptions (1)	(154,305)	[1]
Long-term debt at June 30, 2013 (1)	2,692,235	[1]
Carrying Value of Debt to be Fair Valued [Roll Forward]
Long-term debt at December 31, 2012 (1)	2,561,606	[1]
Payoffs and amortization of long-term debt (1)	(2,115)	[1]
New long-term debt (1)	6,738	[1]
Long-term debt at June 30, 2013 (1)	2,566,229	[1]
Fair Value Above (Below) Carrying Value [Roll Forward]
Long-term debt at December 31, 2012 (1)	280,311	[1]
Changes in fair value assumptions (1)	(154,305)	[1]
Long-term debt at June 30, 2013 (1)	$ 126,006	[1]

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