Fair Value Measurements (Fair Value of Long Term Debt) (Details) (USD $) In Thousands	6 Months Ended
	Jun. 30, 2011		Mar. 31, 2005
Long-term debt, Fair Value	$ 1,304,590
Long-term debt, Carrying Value	1,261,766
Debt Instrument, Unamortized Discount	14,114	[1]
Revolving Credit Facility [Member]
Long-term debt, Fair Value	0
Long-term debt, Carrying Value	0
Long term debt, Maturity Date	July 2015
Term Loan [Member]
Long-term debt, Fair Value	299,998
Long-term debt, Carrying Value	299,250
Long term debt, Maturity Date	July 2015
Convertible Senior Notes [Member]
Long-term debt, Fair Value	299,175
Long-term debt, Carrying Value	300,000	[2]	300,000
Long term debt, Maturity Date	March 2025
Debt Instrument, Unamortized Discount	14,114	[1],[3]
Senior Unsecured Notes [Member]
Long-term debt, Fair Value	583,000
Long-term debt, Carrying Value	550,000
Long term debt, Maturity Date	January 2016
Debt Instrument, Unamortized Discount	0	[1]
MARAD Debt [Member]
Long-term debt, Fair Value	122,417	[4]
Long-term debt, Carrying Value	112,516	[4]
Long term debt, Maturity Date	February 2027
Debt Instrument, Unamortized Discount	$ 0	[1]

[1] The notes will increase to the $300 million face amount through accretion of non-cash interest charges through 2012.

[2] Amount excludes the $14.1 million of unamortized discount recorded on the Convertible Senior Notes at June 30, 2011.

[3] Beginning in December 2012, the holders may require us to repurchase the notes or we may at our own option elect to repurchase the notes. The notes will mature in March 2025.

[4] The estimated fair value of all debt, other than MARAD Debt, was determined using level 1 inputs using the market approach. The fair value of the MARAD debt was determined using a third party evaluation of the remaining average life and outstanding principal balance of the MARAD indebtedness as compared to other governmental obligations in the market place with similar terms. The fair value of the MARAD debt was estimated using level 2 fair value inputs using the cost approach.