Income Taxes - Narratives(Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2014
Operating Loss Carryforwards [Line Items]
Unrecognized tax benefits		$ 4,582	$ 3,549	$ 3,680
Unrecognized tax Benefits that would impact effective tax rate		4,400
Unrecognized tax benefits, penalties and interest expense		200
Uncertain tax benefits, potential change, current		400
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities			6
Valuation allowance		77,437	88,566
Deferred tax assets, research		15,300
Investment tax credit		2,800
IRS
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		178,300	$ 51,500
Foreign
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		$ 3,400
Maximum
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, expiration year		Dec. 31, 2037
CANADA
Operating Loss Carryforwards [Line Items]
Deferred tax assets, research		$ 16,900
Interest Expense [Member]
Operating Loss Carryforwards [Line Items]
Unrecognized tax benefits, accrued tax penalties and interest		1,000
Penalty [Member]
Operating Loss Carryforwards [Line Items]
Unrecognized tax benefits, accrued tax penalties and interest		200
ASU 2016-09
Operating Loss Carryforwards [Line Items]
Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Amount	$ 4,300
ASU 2016-16
Operating Loss Carryforwards [Line Items]
Effect on retained earnings	$ 2,000
Canada Revenue Agency | Foreign
Operating Loss Carryforwards [Line Items]
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities		$ 1,500