Fair Value Measurements Fair Value of Debt (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	$ 1,698,010	$ 1,703,120
Carrying Value	1,578,000	1,545,000
Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value	1,045,000	1,045,000
Convertible Senior Subordinated Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value	250,000	250,000
Subsidiary Revolvers Term Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value	283,000	250,000
Fair Value, Inputs, Level 1 [Member] | Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	1,077,042	1,061,945
Fair Value, Inputs, Level 1 [Member] | Convertible Senior Subordinated Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	350,525	371,975
Fair Value, Inputs, Level 2 [Member] | Subsidiary Revolvers Term Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	$ 270,443	$ 269,200