Debt Convertible Notes (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 08, 2014
Debt Instrument [Line Items]
Interest Expense, Debt, Excluding Amortization	$ 1,400
Gains (Losses) on Extinguishment of Debt	421
Interest Expense, Debt	2,700
Amortization of debt discount (premium)	1,300
Long-term debt	140,311	$ 143,297
Convertible Debt [Member] | Senior 3 Point 25 Percent Convertible Notes Due 2020 [Member]
Debt Instrument [Line Items]
Adjustments to Additional Paid in Capital, Other	4,400
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt, Subsequent Adjustments	500
Interest Expense, Debt, Excluding Amortization	1,400
Gains (Losses) on Extinguishment of Debt	421
Interest Expense, Debt	2,800
Amortization of debt discount (premium)	1,400
Principal amount of Convertible Senior Notes outstanding	167,314	172,500
Unamortized discount of liability component	(23,767)	(25,703)
Unamortized debt issuance costs			$ 4,200
Net carrying amount of liability component	140,311	143,297
Less: current portion	0	0
Long-term debt	140,311	143,297
Carrying value of equity component, net of issuance costs	29,211	29,758		$ 30,700
Fair value of outstanding Convertible Senior Notes	$ 149,746	$ 170,120
Remaining amortization period of discount on the liability component	4 years 9 months	5 years	6 years
Other Current Assets [Member]
Debt Instrument [Line Items]
Unamortized debt issuance costs	$ 300	$ 300
Other Current Assets [Member] | Convertible Debt [Member] | Senior 3 Point 25 Percent Convertible Notes Due 2020 [Member]
Debt Instrument [Line Items]
Unamortized debt issuance costs	(3,236)	3,500
Other non-current assets [Member]
Debt Instrument [Line Items]
Unamortized debt issuance costs	$ 100	$ 200