STOCK-BASED COMPENSATION PLANS - Summary of activity of stock options (Details) - 2016 Stock Incentive Plan - $ / shares	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Shares Under Option
Outstanding at Beginning of Period	11	37	38
Granted	0	0	0
Exercised	(10)	(26)	(1)
Forfeited and cancelled	(1)	0	0
Outstanding at End of Period	0	11	37
Options exercisable at year end	0	11	37
Weighted Average Exercise Price
Outstanding at Beginning of Period	$ 5.49	$ 5.49	$ 5.49
Granted	0	0	0
Exercised	5.49	5.49	5.49
Forfeited and cancelled	5.49	0	0
Outstanding at End of Period	0	5.49	5.49
Options exercisable at year end	$ 0	$ 5.49	$ 5.49

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Gross number of share options (or share units) granted during the period.

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Number of options outstanding, including both vested and non-vested options.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Number of share options (or share units) exercised during the current period.

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