Income Taxes - Net Deferred Income Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred income tax assets
Scientific research and experimental development pool	$ 27,531	$ 26,572
Investment tax credits	24,384	23,808
Non-capital losses	23,603	22,035
Depreciable assets	5,983	5,710
Deferred financing fees	972	1,303
Deferred revenue	8,223
Other	347	203
Less - valuation allowance	(90,805)	(79,526)
Net deferred income tax assets	$ 238	$ 105