Share Capital - Stock Option Activity (Details) $ / shares in Units, $ in Thousands		12 Months Ended
		Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares	Dec. 31, 2019 $ / shares	Dec. 31, 2017 USD ($)
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Options Outstanding, Beginning balance		2,671,906		2,339,905
Number of Options, Granted		1,225,575		706,600
Number of Options, Exercised	[1]	(266,157)		(251,163)
Number of Options, Forfeited, cancelled or expired		(97,088)		(123,436)
Number of Options Outstanding, Ending balance		3,534,236		2,671,906
Number of Options Exercisable, End of period		1,946,026	1,946,026
Weighted Average Exercise Price Outstanding, Beginning balance | (per share)		$ 6.96	$ 9.49	$ 7.41	$ 9.32
Weighted Average Exercise Price, Granted | (per share)		9.43	12.49	5.19	6.73
Weighted Average Exercise Price, Exercised | (per share)	[1]	4.24	5.56	3.53	4.57
Weighted Average Exercise Price, Forfeited, cancelled and expired | (per share)		12.41	16.36	10.50	13.61
Weighted Average Exercise Price Outstanding, Ending balance | (per share)		7.90	$ 10.29	$ 6.96	$ 9.49
Weighted Average Exercise Price, Exercisable Ending balance | (per share)		$ 7.69	$ 7.69			$ 10.02
Aggregate Intrinsic Value, Outstanding | $		$ 19,618	$ 19,618	$ 3,483	$ 3,483		$ 159
Aggregate Intrinsic Value, Exercised | $	[1]	1,594		$ 1,028
Aggregate Intrinsic Value, Exercisable, Ending balance | $		$ 11,755	$ 11,755

[1] During the year ended December 31, 2019, 36,174 (2018 – 49,502) stock options were exercised for the same number of common shares in exchange for cash. In the same period, the Company issued 137,843 (2018 – 106,474) common shares for the cashless exercise of 229,983 (2018 – 201,661) stock options.