Income Taxes - Deferred Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
U.S.
Current income tax expense (benefit)	$ 0	$ 0
Deferred income tax expense (benefit)	0	0
Canada
Current income tax expense (benefit)	0	0
Deferred income tax expense (benefit)	0	0
Other Foreign
Deferred income tax expense (benefit)	$ 0	$ 0