Long-Term Debt (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Carrying value	$ 0	$ 256,995
Carrying value	477,648	400,000
Total long-term debt	477,648	656,995
Less current portion of 2.0% Convertible Senior Notes	0	256,995
Total long-term debt, less current portion	477,648	400,000
2.0% Convertible Senior Notes, due May 15, 2012 [Member]
Debt Instrument [Line Items]
Carrying value	0	256,995
Total long-term debt	0	256,995
7.5% Senior Notes, due November 15, 2019 [Member]
Debt Instrument [Line Items]
Carrying value	477,648	400,000
Total long-term debt	$ 477,648	$ 400,000