Derivative Financial Instruments (Details) (USD $)	3 Months Ended		12 Months Ended
	Dec. 31, 2010	Jun. 30, 2010	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Oct. 07, 2010	Jun. 02, 2010	Jun. 01, 2010
Derivative [Line Items]
Unamortized Loss on Derivative Instruments	$ 81,500,000			$ 72,000,000	$ 81,500,000
Loss on settlement of derivative instruments	36,700,000	26,800,000
Notional Amount of Interest Rate Cash Flow Hedge Derivatives									150,000,000
Notional Amount of Interest Rate Derivatives						290,700,000	140,700,000
Debt Instrument, Face Amount							250,000,000	150,000,000
Debt Instrument, Interest Rate, Stated Percentage							4.80%	6.00%
Derivative, Loss on Derivative				(54,000)		(3,300,000)
Derivative, Gain on Derivative					1,400,000
Derivative, Inception Date				Oct. 01, 2011
Derivative, Notional Amount				9,000
Derivative, Description of Variable Rate Basis				1 Month LIBOR
Derivative, Fixed Interest Rate				0.76%
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months			$ 9,500,000
Debt Instrument, Interest Rate, Effective Percentage							6.26%	7.67%