Fair Value of Financial Instruments (Details 2) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Reconciliation of financial liabilities measured at fair value using significant unobservable inputs (Level 3)
Balance, at beginning of period			$ 89,888
Change in fair value of derivative instruments	2,220	27,234	7,818	28,723
Redemption of a portion of the 2012 notes			(5,602)
Balance, at ending of period	$ 92,104		$ 92,104