NOTES PAYABLE AND AMENDED CREDIT AGREEMENT - Summary of Notes Payable and Credit Agreement (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Payments/Long term debt, Total	$ 48,099	$ 60,772
Less current portion	(5,317)	(4,044)
Long term portion	42,782	56,728
Credit Facility [Member]
Debt Instrument [Line Items]
Payments/Long term debt, Total	$ 42,000	54,000
Average effective interest rate	3.80%
3.25% through 4.25% Notes Payable due in Next Year [Member]
Debt Instrument [Line Items]
Payments/Long term debt, Total	$ 6,099	$ 6,772
Annual installments	$ 5,317
3.25% through 4.25% Notes Payable due in Next Year [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Percentage of interest accrued	3.25%
3.25% through 4.25% Notes Payable due in Next Year [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Percentage of interest accrued	4.25%

Amount of the total principal payments made during the annual reporting period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Contractual interest rate for funds borrowed, under the debt agreement.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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The effective interest rate during the reporting period.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Section S99
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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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