CAPITAL STOCK AND SHARE-BASED COMPENSATION - Non-Vested Stock Option Activity (Details)	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Number of Shares
Non-vested stock options beginning balance (shares) | shares	527,798
Granted (shares) | shares	163,666
Vested (shares) | shares	(246,442)
Forfeited (shares) | shares	(74,552)
Non-vested stock options ending balance (shares) | shares	370,470
Weighted Average Grant Date Fair Value
Non-vested stock options beginning balance (usd per share) | $ / shares	$ 23.00
Granted (usd per share) | $ / shares	42.48
Vested (usd per share) | $ / shares	23.11
Forfeited (usd per share) | $ / shares	25.78
Non-vested stock options ending balance (usd per share) | $ / shares	$ 30.97