Debt (Details 1)	9 Months Ended
Sep. 30, 2018 USD ($)
Line of Credit Facility
Letters of Credit Outstanding, Amount	$ 5,724,000
Line of Credit Facility, Commitment Fee Amount	$ 455,000
Debt, Weighted Average Interest Rate	5.40%
Debt, Weighted Average Interest Rate, net of Currency Swap Contract	4.50%
Revolving Credit Facility
Line of Credit Facility
Outstanding Borrowings	$ 20,000,000
Debt Instrument, Unused Borrowing Capacity, Amount	180,000,000
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	6,250,000
Long-term Debt, Additional Repayments of Principal in Next Twelve Months	23,750,000
Long-term Debt, Current Maturities	$ 30,000,000
Revolving Credit Facility \| JPMorgan, 2017 Credit Agreement
Line of Credit Facility
Debt Instrument, Covenant, Indebtedness to Adjusted EBITDA Ratio, Maximum	4.00
Debt Instrument, Covenant, Adjusted EBITDA to Interest Expense Ratio, Maximum	3.50
Debt Instrument, Covenant, Senior Secured Net Indebtedness to Adjusted EBITDA Ratio, Maximum	3.50
Debt Instrument, Covenant, Net Leverage Ratio, Minimum	3.00
Line of Credit
Line of Credit Facility
Outstanding Borrowings	$ 30,000,000
Letter of Credit
Line of Credit Facility
Debt Instrument, Unused Borrowing Capacity, Amount	$ 174,276,000
Minimum \| Revolving Credit Facility \| JPMorgan, 2017 Credit Agreement
Line of Credit Facility
Debt Instrument, Covenant, Repayment of Debt, Percentage of Excess Cash Flow	25.00%
Maximum \| Revolving Credit Facility \| JPMorgan, 2017 Credit Agreement
Line of Credit Facility
Debt Instrument, Covenant, Repayment of Debt, Percentage of Excess Cash Flow	50.00%

Debt Instrument, Covenant, Adjusted EBITDA to Interest Expense Ratio, Maximum

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Debt Instrument, Covenant, Indebtedness to Adjusted EBITDA Ratio, Maximum

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- Definition

Debt Instrument, Covenant, Net Leverage Ratio, Minimum

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Debt Instrument, Covenant, Repayment of Debt, Percentage of Excess Cash Flow

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Debt Instrument, Covenant, Senior Secured Net Indebtedness to Adjusted EBITDA Ratio, Maximum

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- Definition

Weighted average interest rate of debt outstanding, net of currency swap contract.

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- Definition

Long-term Debt, Additional Repayments of Principal in Next Twelve Months

+ References

No definition available.

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- Definition

Amount of unused borrowing capacity under the long-term financing arrangement that is available to the entity as of the balance sheet date.

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Weighted average interest rate of debt outstanding.

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- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

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- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

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

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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- Definition

Amount of the fee for available but unused credit capacity under the credit facility.

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- Definition

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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- Definition

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.

+ References

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- Definition

Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04.(a))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601

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