Earnings (Loss) per Share - Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Basic and diluted loss per share
Net loss for the period	$ (15,441)	$ (23,259)	$ (21,707)	$ (20,217)	$ (38,700)	$ (41,924)
Weighted average number of shares outstanding	112,778,258		72,526,441		103,686,706	70,624,583
Basic and diluted loss per share	$ (0.14)		$ (0.30)		$ (0.37)	$ (0.59)