Notes Payable - Summary of Notes Payable (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Payments/Long term debt, Total	$ 60,772	$ 51,823
Less current portion	(4,044)	(1,227)
Long term portion	56,728	50,596
Credit Facility [Member]
Debt Instrument [Line Items]
Payments/Long term debt, Total	$ 54,000	46,000
Average effective interest rate	3.60%
3.25 % through 4.25 % notes payable due in next year [Member]
Debt Instrument [Line Items]
Payments/Long term debt, Total	$ 6,772	$ 5,823
Annual installments	$ 4,044
3.25 % through 4.25 % notes payable due in next year [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Percentage of interest accrued	4.25%
3.25 % through 4.25 % notes payable due in next year [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Percentage of interest accrued	3.25%

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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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
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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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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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