Debt Convertible Notes (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2014	Dec. 08, 2014
Debt Instrument [Line Items]
Interest Expense, Debt, Excluding Amortization	$ 1,400
Gain on extinguishment of Convertible Senior Notes		$ (421)
Interest Expense, Debt	2,800
Amortization of debt discount (premium)	1,400
Long-term debt	145,705		$ 144,340
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
Gain on extinguishment of Convertible Senior Notes	(400)
Interest Expense, Debt	2,800
Amortization of debt discount (premium)	1,400
Principal amount of Convertible Senior Notes outstanding	167,314		167,314
Unamortized discount of liability component	(19,020)		(20,221)
Unamortized debt issuance costs				$ (4,200)
Net carrying amount of liability component	145,705		144,340
Less: current portion	0		0
Long-term debt	145,705		144,340
Carrying value of equity component, net of issuance costs	29,211		29,211		$ 30,700
Fair value of outstanding Convertible Senior Notes	$ 170,961		$ 165,223
Remaining amortization period of discount on the liability component	3 years 9 months		4 years	6 years
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	$ (2,589)		$ (2,753)