STOCK PLANS - Restricted Stock and Restricted Stock Unit Activity (Details) - $ / shares	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restricted Stock and Restricted Stock Units
Outstanding at beginning of year (in shares)	993,962
Outstanding at end of year (in shares)	841,610	993,962
Restricted Stock And Restricted Stock Units
Restricted Stock and Restricted Stock Units
Granted (in shares)	548,301	586,141	314,360
Restricted Stock And Restricted Stock Units \| Cliff - Subject to service conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Period		3 years	3 years
Restricted Stock and Restricted Stock Units
Granted (in shares)	277,250	283,000	146,000
Weighted-Average Fair Value
Granted (in dollars per share)	$ 22.80	$ 18.69	$ 21.64
Restricted Stock And Restricted Stock Units \| Graded - Subject to service conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Period	3 years	3 years	3 years
Restricted Stock and Restricted Stock Units
Granted (in shares)	24,488	30,632	22,360
Weighted-Average Fair Value
Granted (in dollars per share)	$ 22.87	$ 18.28	$ 21.31
Restricted Stock And Restricted Stock Units \| Cliff - Subject to service and performance conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Period	3 years	3 years	3 years
Restricted Stock and Restricted Stock Units
Granted (in shares)	147,938	163,509	73,000
Weighted-Average Fair Value
Granted (in dollars per share)	$ 22.77	$ 18.81	$ 21.64
Restricted Stock And Restricted Stock Units \| Cliff - Subject to service and market conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Period	3 years	3 years	3 years
Restricted Stock and Restricted Stock Units
Granted (in shares)	98,625	109,000	73,000
Weighted-Average Fair Value
Granted (in dollars per share)	$ 15.86	$ 12.65	$ 14.62
Restricted Stock
Restricted Stock and Restricted Stock Units
Outstanding at beginning of year (in shares)	993,962
Granted (in shares)	301,738
Forfeited (in shares)	(61,480)
Vested (in shares)	(392,610)
Outstanding at end of year (in shares)	841,610	993,962
Weighted-Average Fair Value
Outstanding at beginning of year (in dollars per share)	$ 18.00
Granted (in dollars per share)	22.80
Forfeited (in dollars per share)	20.88
Vested (in dollars per share)	16.07
Outstanding at end of year (in dollars per share)	$ 20.41	$ 18.00
Restricted Stock Units
Restricted Stock and Restricted Stock Units
Outstanding at beginning of year (in shares)	30,000	45,000	80,000
Vested (in shares)	(15,000)	(15,000)	(35,000)
Outstanding at end of year (in shares)	15,000	30,000	45,000
Weighted-Average Fair Value
Outstanding at beginning of year (in dollars per share)	$ 14.04	$ 14.04	$ 14.04
Vested (in dollars per share)	14.04	14.04	14.04
Outstanding at end of year (in dollars per share)	$ 14.04	$ 14.04	$ 14.04
Restricted Stock Units, Performance Based
Restricted Stock and Restricted Stock Units
Outstanding at beginning of year (in shares)	535,105	380,458	323,083
Granted (in shares)	147,938	163,509	73,000
Forfeited (in shares)	(39,347)	(8,862)	(15,625)
Vested (in shares)	(316,210)
Outstanding at end of year (in shares)	327,486	535,105	380,458
Weighted-Average Fair Value
Outstanding at beginning of year (in dollars per share)	$ 18.45	$ 18.28	$ 17.36
Granted (in dollars per share)	22.77	18.81	21.64
Forfeited (in dollars per share)	21.03	17.93	15.92
Vested (in dollars per share)	17.70
Outstanding at end of year (in dollars per share)	$ 20.44	$ 18.45	$ 18.28
Restricted Stock Units, Market Based
Restricted Stock and Restricted Stock Units
Outstanding at beginning of year (in shares)	262,609	160,812	103,437
Granted (in shares)	98,625	109,000	73,000
Forfeited (in shares)	(28,657)	(7,203)	(15,625)
Vested (in shares)	(95,869)
Outstanding at end of year (in shares)	236,708	262,609	160,812
Weighted-Average Fair Value
Outstanding at beginning of year (in dollars per share)	$ 11.96	$ 10.12	$ 8.18
Granted (in dollars per share)	15.86	13.02	12.14
Forfeited (in dollars per share)	13.83	11.42	8.93
Vested (in dollars per share)	8.97
Outstanding at end of year (in dollars per share)	$ 14.40	$ 11.96	$ 10.12
Minimum [Member] \| Restricted Stock And Restricted Stock Units \| Cliff - Subject to service conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Period	3 years
Maximum \| Restricted Stock And Restricted Stock Units \| Cliff - Subject to service conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Period	4 years

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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- Definition

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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-Publisher FASB
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- Definition

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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No definition available.

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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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-Name Accounting Standards Codification
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- Definition

The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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