Share Capital - Stock Option Activity (Details) - shares		3 Months Ended		9 Months Ended		12 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding, beginning of period		2,276,897	1,983,674	1,910,823	1,721,472	1,721,472
Granted		1,050	22,044	447,550	321,444
Exercised	[1]		(42,012)	(71,006)	(72,541)
Forfeited and expired		(70,567)	(4,753)	(79,987)	(11,422)
Outstanding, end of period		2,207,380	1,958,953	2,207,380	1,958,953	1,910,823
Exercisable, end of period		1,417,660	1,200,614	1,417,660	1,200,614

[1] During the nine months ended September 30, 2017, 63,425 stock options were exercised for the same number of common shares for cash (nine months ended September 30, 2016 – 30,176). In the same period, the Company issued 4,405 common shares (nine months ended September 30, 2016 – 27,421) for the cashless exercise of 7,581 stock options (nine months ended September 30, 2016 – 42,365).