Earnings (Loss) per Share - Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Basic and diluted loss per share
Net loss for the period	$ (12,951)	$ (15,441)	$ (23,259)	$ (17,795)	$ (21,707)	$ (20,217)	$ (51,651)	$ (59,719)
Weighted average number of shares outstanding	144,690,904			75,161,192			117,454,536	72,153,405
Basic and diluted loss per share	$ (0.09)			$ (0.24)			$ (0.44)	$ (0.83)