Stock Option Plan - Stock Option Activity (Details) - shares		3 Months Ended		6 Months Ended		12 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding, beginning of period		1,934,734	1,785,436	1,721,472	1,484,218	1,484,218
Granted		65,450	33,474	299,400	380,438
Exercised	[1]	(14,283)	(55,155)	(30,529)	(99,811)
Forfeited and expired		(2,227)	(18,737)	(6,669)	(19,827)
Outstanding, end of period		1,983,674	1,745,018	1,983,674	1,745,018	1,721,472
Exercisable, end of period		1,195,883	1,126,629	1,195,883	1,126,629

[1] During the six months ended June 30, 2016, 29,270 stock options were exercised for the same number of common shares for cash (six months ended June 30, 2015 – 53,442). In the same period, the Company issued 741 common shares (six months ended June 30, 2015 – 32,399) for the cashless exercise of 1,259 stock options (six months ended June 30, 2015 – 46,369).