Debt Convertible Notes (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 08, 2014
Debt Instrument [Line Items]
Interest Expense, Debt, Excluding Amortization	$ 4,200
Gain on extinguishment of Convertible Senior Notes		$ (421)	$ 0
Interest Expense, Debt	8,200
Amortization of debt discount (premium)	4,000
Long-term debt	142,986	142,986		$ 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		4,100
Gain on extinguishment of Convertible Senior Notes	(400)
Interest Expense, Debt		8,200
Amortization of debt discount (premium)		4,100
Principal amount of Convertible Senior Notes outstanding	167,314	167,314		172,500
Unamortized discount of liability component	(21,413)	(21,413)		(25,703)
Unamortized debt issuance costs					$ (4,200)
Net carrying amount of liability component	142,986	142,986		143,297
Less: current portion	0	0		0
Long-term debt	142,986	142,986		143,297
Carrying value of equity component, net of issuance costs	29,211	29,211		29,758		$ 30,700
Fair value of outstanding Convertible Senior Notes	168,054	$ 168,054		$ 170,120
Remaining amortization period of discount on the liability component		4 years 3 months		5 years	6 years
Other Current Assets [Member]
Debt Instrument [Line Items]
Unamortized debt issuance costs	(300)	$ (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	$ (2,915)	$ (2,915)		(3,500)
Other non-current assets [Member]
Debt Instrument [Line Items]
Unamortized debt issuance costs				$ (200)