Long Term Debt Long Term Debt (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Debt Instrument [Line Items]
Long-term debt	$ 604,273		$ 601,746
Allocated Share-based Compensation Expense	3,614	$ 2,809
Unamortized Debt Issuance Expense	(7,389)		(7,757)
Long-term Debt, Current Maturities	0		0
Total long-term debt, less current portion	604,273		601,746
Long-term Debt, Fair Value	$ 803,800		792,200
Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Issuance Date	Jul. 26, 2012
Debt Instrument, Face Amount	$ 250,000
Debt Instrument, Interest Rate, Stated Percentage	8.00%
Debt Instrument, Maturity Date	Aug. 01, 2020
Proceeds from Debt, Net of Issuance Costs	$ 245,000
Debt Instrument, Unamortized Discount	$ 5,000
Debt Instrument, Frequency of Periodic Payment	semi-annually
Debt Instrument, Call Date, Earliest	Aug. 01, 2016
Long-term debt	$ 247,521		247,359
Long-term Debt, Fair Value	$ 259,400		275,400
Convertible Debt Securities [Member]
Debt Instrument [Line Items]
Debt Instrument, Issuance Date	Jun. 10, 2014
Debt Instrument, Face Amount	$ 402,500
Debt Instrument, Interest Rate, Stated Percentage	3.25%
Debt Instrument, Maturity Date	Jun. 15, 2029
Debt Instrument, Unamortized Discount	$ 59,000
Debt Instrument, Convertible, Remaining Discount Amortization Period	4 years 2 months 16 days
Debt Instrument, Frequency of Periodic Payment	semiannually
Debt Instrument, Convertible, Carrying Amount of Equity Component	$ 37,700
Long-term debt	364,141		362,144
Long-term Debt, Fair Value	$ 544,400		$ 516,800