CAPITAL 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
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate (as a percent)	1.17%	1.17%	1.19%	1.16%
Expected lives (in years)	4 years 5 months 18 days	3 years 4 months 24 days	4 years 5 months 18 days	3 years 4 months 24 days
Expected volatility (as a percent)	41.00%	43.00%	41.00%	43.00%
Expected dividend rate (as a percent)	0.00%	0.00%	0.00%	0.00%
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at beginning of period			940,610	1,074,251	1,074,251
Granted at Market			19,355		146,446
Canceled			(463)		(28,440)
Exercised			(70,507)		(251,647)
Outstanding at end of period	888,995		888,995		940,610
Exercisable at end of period	633,469		633,469		621,559
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Outstanding at beginning of period (in dollars per share)			$ 14.163	$ 10.110	$ 10.110
Granted at Market (in dollars per share)			39.074		36.904
Cancelled (in dollars per share)			14.881		10.080
Exercised (in dollars per share)			11.793		10.559
Outstanding at ending of period (in dollars per share)	$ 14.893		14.893		14.163
Exercisable at end of period (in dollars per share)	$ 11.489		$ 11.489		$ 10.269
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate (as a percent)	0.55%	0.24%	0.53%	0.24%
Expected lives (in years)	1 year 2 months 18 days	1 year 2 months 18 days	1 year 2 months 18 days	1 year 2 months 18 days
Expected volatility (as a percent)	43.00%	36.00%	42.00%	35.00%
Expected dividend rate (as a percent)	0.00%	0.00%	0.00%	0.00%

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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- Definition

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.