SHARE-BASED COMPENSATION PLANS - Award Plan (Details)	12 Months Ended
Dec. 31, 2017 shares day	Dec. 31, 2016 shares
Restricted Awards
Disclosure of terms and conditions of share-based payment arrangement [line items]
Vesting period	3 years
Number of trading days to determine weighted average trading price for instruments granted \| day	5
Number of instruments outstanding, beginning of period (in shares)	426,395	318,762
Number of instruments granted (in shares)	652,740	284,771
Number of instruments exercised (in shares)	(175,833)	(113,457)
Number instruments forfeited (in shares)	(79,815)	(63,681)
Number of instruments outstanding, end of period (in shares)	823,487	426,395
Performance Awards
Disclosure of terms and conditions of share-based payment arrangement [line items]
Number of trading days to determine weighted average trading price for instruments granted \| day	5
Forfeiture rate	5.00%
Number of instruments outstanding, beginning of period (in shares)	303,335	249,240
Number of instruments granted (in shares)	370,000	145,085
Number of instruments exercised (in shares)	(61,920)	(70,430)
Number instruments forfeited (in shares)	(38,360)	(20,560)
Number of instruments outstanding, end of period (in shares)	573,055	303,335
Bottom of range \| Restricted Awards
Disclosure of terms and conditions of share-based payment arrangement [line items]
Forfeiture rate	3.00%
Bottom of range \| Performance Awards
Disclosure of terms and conditions of share-based payment arrangement [line items]
Payout multiplier	0.00%
Top of range \| Restricted Awards
Disclosure of terms and conditions of share-based payment arrangement [line items]
Forfeiture rate	10.00%
Top of range \| Performance Awards
Disclosure of terms and conditions of share-based payment arrangement [line items]
Payout multiplier	200.00%

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The number of other equity instruments (ie other than share options) granted in a share-based payment arrangement.

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