Anniversary when principal payments begin

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- Definition

Debt Instrument, Variable Rate, Base Rate Calculation

+ References

No definition available.

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- Definition

debt instrument variable rate base rate calculation, default rate

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- Definition

Letter of credit, unused capacity, commitment fee percentage

+ References

No definition available.

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- Definition

Number of principal payments

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No definition available.

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- Definition

Unused commitment fee threshold percent

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- Definition

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

+ References

No definition available.

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- Definition

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

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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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No definition available.

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- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ 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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Balance Type:	credit
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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 current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

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- Definition

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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- Definition

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

+ References

No definition available.

+ Details

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Long-Term Debt and Commitments Related to Letters of Credit (Narrative) (Details)	3 Months Ended
	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	May 07, 2017 USD ($)
Debt Instrument [Line Items]
Revolving credit facility, current borrowing capacity	$ 250,000,000
Revolving credit facility, maximum borrowing capacity	325,000,000
Unused commitments under credit facility	118,587,000
Revolving credit facility borrowings	$ 128,500,000	$ 100,000,000
Number of principal payments	5
Anniversary when principal payments begin	6
Minimum [Member]
Debt Instrument [Line Items]
Line of credit facility, unused capacity, commitment fee percentage	0.10%
Maximum [Member]
Debt Instrument [Line Items]
Line of credit facility, unused capacity, commitment fee percentage	0.225%
Swing-line borrowings [Member]
Debt Instrument [Line Items]
Revolving credit facility, current borrowing capacity	$ 25,000,000
Revolving credit facility borrowings	$ 13,500,000	$ 0
Unsecured debt [Member]
Debt Instrument [Line Items]
Interest rate	5.09%
Accounts receivable securitization [Member]
Debt Instrument [Line Items]
Interest rate	0.90%
Unused commitment fee threshold percent	0.50
Debt instrument variable rate base rate calculation, default rate	2.00%
Accounts receivable securitization [Member] \| Base Rate, Federal Funds [Member]
Debt Instrument [Line Items]
Debt instrument, variable rate, base rate calculation	0.50%
Line of credit [Member]
Debt Instrument [Line Items]
Revolving credit facility borrowings	$ 131,413,000
Line of credit [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Debt instrument, variable rate, base rate calculation	1.50%
Line of credit [Member] \| Base Rate, Federal Funds [Member]
Debt Instrument [Line Items]
Debt instrument, variable rate, base rate calculation	0.50%
Line of credit [Member] \| Minimum [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Outstanding borrowings interest rate margin adjustment, range	0.875%
Line of credit [Member] \| Maximum [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Outstanding borrowings interest rate margin adjustment, range	1.50%
Letter of credit [Member]
Debt Instrument [Line Items]
Letters of credit issued	$ 63,067,000
Letter of credit [Member] \| Revolving credit facility [Member]
Debt Instrument [Line Items]
Letters of credit issued	2,913,000
Letter of credit [Member] \| Accounts receivable securitization [Member]
Debt Instrument [Line Items]
Revolving credit facility, maximum borrowing capacity	100,000,000		$ 60,000,000
Letters of credit issued	$ 58,150,000
Debt Instrument, Term	1 year
Letter of credit [Member] \| Accounts receivable securitization [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Letter of credit, unused capacity, commitment fee percentage	0.0035
Letter of credit [Member] \| Accounts receivable securitization [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Letter of credit, unused capacity, commitment fee percentage	0.0045
Letter of credit [Member] \| Line of credit [Member]
Debt Instrument [Line Items]
Letters of credit issued	$ 2,004,000
Letter of credit [Member]
Debt Instrument [Line Items]
Revolving credit facility, maximum borrowing capacity	$ 100,000,000