Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income taxes
Pre-change net operating losses that can be used in future years	$ 13,500
Net operating losses not subject to IRC section 382	223,100
Deferred tax assets, U.S. net operating loss carryforwards	236,600
Unused net operating loss carryforwards	27,700	$ 42,200
Amount of net operating loss carryforwards that will expire due to IRC Section 382 limitations	2,600
Net operating loss carryforwards	64,523	58,364
Un-repatriated foreign earnings	0
Canada
Income taxes
Research and experimental development expenditure carryforwards	17,200
Canadian ITC credit carryforwards	1,300
U.S.
Income taxes
Net operating loss carryforwards	54,947	49,058
Foreign
Income taxes
Net operating loss carryforwards	9,576	$ 9,306
Foreign | French
Income taxes
Unused net operating loss carryforwards	17,900
Foreign | Canada
Income taxes
Net operating loss carryforwards	$ 14,000