Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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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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The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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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.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Stock Plans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017
Stock Option Plans
Defined Benefit Plan Disclosure [Line Items]
Shares of common stock available for issuance (in shares)	1,700,000		1,700,000
Compensation expense	$ 2,599	$ 2,096	$ 5,374	$ 4,590
Income tax benefits	$ 650	$ 807	$ 1,344	$ 1,767
Stock Option Plans \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Vesting period of options			3 years
Expiration period of grant			6 years
Stock Option Plans \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Vesting period of options			7 years
Expiration period of grant			10 years
Restricted Stock Units (RSUs)
Defined Benefit Plan Disclosure [Line Items]
Vesting period of options			3 years