Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
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Derivative, Notional Amount, Quarterly Reduction, Amount. Expressed as an absolute value.

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Leverage Ratio

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Credit Facility Fixed Charge Coverage Ratio

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Maximum possible value of increase in maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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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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Amount of the required periodic payments including both interest and principal payments.

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Weighted average interest rate of debt outstanding.

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Fixed interest rate related to the interest rate derivative.

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Period the derivative contract is outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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

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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.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

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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/disclosureRef
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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.

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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 fifth 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.

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Long-term Debt and Financing Arrangements - Narrative (Details)		1 Months Ended		3 Months Ended	9 Months Ended	57 Months Ended
	Aug. 31, 2018 USD ($)	Nov. 30, 2018 USD ($)	Apr. 30, 2017 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2023 USD ($)	Aug. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016	Jul. 06, 2016 USD ($)
Debt Instrument [Line Items]
Long-term debt				$ 324,813,000				$ 77,190,000
Long-term debt maturing in 2019				10,200,000
Long-term debt maturing in 2020				9,900,000
Long-term debt maturing in 2021				9,900,000
Long-term debt maturing in 2022				9,900,000
Long-term debt maturing in 2023				$ 284,900,000
Weight-average interest rate (as a percent)				3.40%				2.20%	1.40%
Term Loan Due August 31, 2023
Debt Instrument [Line Items]
Long-term debt					$ 200,000,000
Amended Credit Facility
Debt Instrument [Line Items]
Long-term debt					$ 250,000,000
Letters of credit outstanding				$ 3,900,000
Amended Credit Facility \| Revolving Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 450,000,000						$ 175,000,000			$ 450,000,000
Maximum borrowing capacity possible value of increase (not to exceed)	$ 150,000,000
Minimum fixed charge coverage ratio for preceding 12 month period					1.25
Maximum leverage ratio of credit facility					3.5
Remaining borrowing availability				108,100,000
Borrowings outstanding				138,000,000
Amended Credit Facility \| Revolving Credit Facility \| Minimum
Debt Instrument [Line Items]
Unused borrowing capacity, commitment fee percentage					0.15%
Amended Credit Facility \| Revolving Credit Facility \| Maximum
Debt Instrument [Line Items]
Unused borrowing capacity, commitment fee percentage					0.275%
Amended Credit Facility \| Revolving Credit Facility \| Federal Funds Effective Swap Rate
Debt Instrument [Line Items]
Basis spread (as a percent)					0.50%
Amended Credit Facility \| Revolving Credit Facility \| Base Rate \| Minimum
Debt Instrument [Line Items]
Basis spread (as a percent)					0.00%
Amended Credit Facility \| Revolving Credit Facility \| Base Rate \| Maximum
Debt Instrument [Line Items]
Basis spread (as a percent)					1.25%
Amended Credit Facility \| Revolving Credit Facility \| Eurocurrency Rate
Debt Instrument [Line Items]
Basis spread (as a percent)					1.00%
Amended Credit Facility \| Revolving Credit Facility \| Eurocurrency Rate \| Minimum
Debt Instrument [Line Items]
Basis spread (as a percent)					0.75%
Amended Credit Facility \| Revolving Credit Facility \| Eurocurrency Rate \| Maximum
Debt Instrument [Line Items]
Basis spread (as a percent)					2.00%
Amended Credit Facility \| Foreign Credit Facilities
Debt Instrument [Line Items]
Remaining borrowing availability				8,200,000
Letters of credit outstanding				2,200,000
Interest rate contracts
Debt Instrument [Line Items]
Term of derivative contract		5 years	3 years
Notional amount of derivative		$ 139,000,000.0	$ 60,000,000.0
Derivative fixed interest rate (as a percent)		3.09%	1.58%
Derivative quarterly reduction amount				$ 5,000,000.0
Subsequent Event \| Term Loan Due August 31, 2023
Debt Instrument [Line Items]
Periodic payment on debt instrument						$ 2,500,000