Share Capital - Stock Option Activity (Details) - shares		3 Months Ended		6 Months Ended		12 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding, beginning of period		2,258,237	1,934,734	1,910,823	1,721,472	1,721,472
Granted		29,750	65,450	446,500	299,400
Exercised	[1]	(3,085)	(14,283)	(71,006)	(30,529)
Forfeited and expired		(8,005)	(2,227)	(9,420)	(6,669)
Outstanding, end of period		2,276,897	1,983,674	2,276,897	1,983,674	1,910,823
Exercisable, end of period		1,374,535	1,195,883	1,374,535	1,195,883

[1] During the six months ended June 30, 2017, 63,425 stock options were exercised for the same number of common shares for cash (six months ended June 30, 2016 – 29,270). In the same period, the Company issued 4,405 common shares (six months ended June 30, 2016 – 741) for the cashless exercise of 7,581 stock options (six months ended June 30, 2016 – 1,259).