Capital lease obligation period.

No definition available.

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Period Type:	duration

- Definition

Debt instrument maximum authorized value.

+ References

No definition available.

+ Details

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Period Type:	instant

- Definition

Line of credit facility additional borrowing capacity.

+ References

No definition available.

+ Details

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- Definition

Line of credit facility amended expiration month and year.

+ References

No definition available.

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- Definition

Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84164817&loc=d3e45280-112737

Reference 2: 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 3: 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(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt 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(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Description of the interest rate as being fixed or variable, and, if variable, identification of the index or rate on which the interest rate is based and the number of points or percentage added to that index or rate to set the rate, and other pertinent information, such as frequency of rate resets.

+ References

+ Details

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Balance Type:	na
Period Type:	duration

- 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.

+ References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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.

+ 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 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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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Balance Type:	na
Period Type:	duration

- Definition

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.

+ References

Reference 1: 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(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Balance Type:	credit
Period Type:	instant

- Definition

Weighted average interest rate of long-term debt outstanding calculated at point in time.

+ References

No definition available.

+ Details

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- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

+ References

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Balance Type:	credit
Period Type:	instant

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- Details

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- Details

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Debt and Financing Arrangements - Additional Information (Detail) - USD ($)		6 Months Ended
	Mar. 06, 2015	Jun. 30, 2017	Dec. 31, 2016	Mar. 05, 2015	Jan. 31, 2008	Nov. 30, 2007	Apr. 30, 2005	Dec. 31, 2002
Debt Instrument [Line Items]
Letter of credit facility outstanding amount		$ 1,800,000
Senior notes outstanding		3,571,000	$ 7,143,000
Capital Leases, described below		$ 89,783,000	$ 66,661,000
Lease expiration period		7 years
Banking Group [Member]
Debt Instrument [Line Items]
Credit Agreement with Banks		$ 55,014,000
Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Weighted average interest rate for capital lease		3.03%	2.82%
Credit Agreement [Member] \| Revolving Credit Facility [Member] \| Credit Agreement Before Amendments [Member]
Debt Instrument [Line Items]
Borrowing capacity under credit agreement				$ 200,000,000
Restated Credit Agreement [Member]
Debt Instrument [Line Items]
Amendment line of credit facility expiration year and month	2020-03
Restated Credit Agreement [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Borrowing capacity under credit agreement	$ 250,000,000
Additional borrowing capacity under revolving credit facility		$ 75,000,000
Credit Agreement with Banks		55,000,000	$ 0
Letter of credit facility outstanding amount		$ 33,900,000	39,400,000
Restated Credit Agreement [Member] \| Revolving Credit Facility [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Letter of credit unused portion fee		0.20%
Restated Credit Agreement [Member] \| Revolving Credit Facility [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Letter of credit unused portion fee		0.30%
Restated Credit Agreement [Member] \| Revolving Credit Facility [Member] \| LIBOR Rate Margin [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Rate margin		1.125%
Restated Credit Agreement [Member] \| Revolving Credit Facility [Member] \| Banking Group [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Rate margin		1.125%
Restated Credit Agreement [Member] \| Revolving Credit Facility [Member] \| Banking Group [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Rate margin		2.25%
Restated Credit Agreement [Member] \| Revolving Credit Facility [Member] \| Banking Group [Member] \| LIBOR Rate Margin [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Rate margin		2.25%
Restated Credit Agreement [Member] \| Revolving Credit Facility [Member] \| Banking Group [Member] \| Base Rate Margin [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Rate margin		0.125%
Restated Credit Agreement [Member] \| Revolving Credit Facility [Member] \| Banking Group [Member] \| Base Rate Margin [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Rate margin		0.50%
Restated Master Shelf Agreement [Member]
Debt Instrument [Line Items]
Senior notes outstanding		$ 3,600,000	$ 7,100,000
Restated Master Shelf Agreement [Member] \| Senior Notes under Master Shelf Agreement [Member]
Debt Instrument [Line Items]
Senior notes issued, value					$ 25,000,000	$ 25,000,000		$ 100,000,000
Senior notes authorized amount							$ 150,000,000	$ 125,000,000
Interest rate on notes					6.17%	6.14%
Senior credit facility, Interest rate terms description		The November 2007 issuance of $25 million Senior Notes has a fixed interest rate of 6.14 percent. The January 2008 issuance of $25 million Senior Notes has a fixed interest rate of 6.17 percent. Payments due for both $25 million issuances were interest only until June 30, 2011 and at that time semi-annual principal payments began with the final payments due January 1, 2018.