Fair Value Measurements Fair Value of Debt (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Fair Value	$ 1,694,932	$ 1,495,353
Carrying Value	1,354,667	1,346,651
Quoted Prices in Active Markets for Identical Assets | Senior Notes
Debt Instrument [Line Items]
Fair Value	792,600	737,049
Carrying Value	745,000	745,000
Quoted Prices in Active Markets for Identical Assets | Convertible Senior Subordinated Debt
Debt Instrument [Line Items]
Fair Value	533,750	405,625
Carrying Value	250,000	250,000
Significant Unobservable Inputs | Subsidiary Term Loans
Debt Instrument [Line Items]
Fair Value	368,582	352,679
Carrying Value	$ 359,667	$ 351,651