Revolving Credit Facility (Details Textual) (USD $)	3 Months Ended
Mar. 31, 2013
Revolving Credit Facility (Additional Textual) [Abstract]
Line of credit facility expiration date	Oct. 01, 2017
Revolving credit facility borrowing capacity	$ 24,000,000
Letters of credit outstanding amount	23,800,000
LIBOR plus rate	1.75%
Interest calculation under revolving credit facility	The Agreement also provides for an unused commitment fee of 0.25% per annum on the average daily unused amount of the revolving credit facility
Reduction in maximum borrowing capacity	2,500,000
Ratio of restricted and unrestricted cash and marketable securities to workers compensation and safety incentive liabilities	1.0
Prohibition on incurring additional indebtedness without the prior approval of the Bank in purchase money financing	200,000
Revolving Credit Facility [Member]
Revolving Credit Facility (Textual) [Abstract]
Outstanding borrowings on the revolving credit facility	$ 0
Interest calculation under revolving credit facility	The rate is calculated based on LIBOR plus 1.75%.
Interest rate under revolving credit facility	0.25%
September 30, 2014 [Member]
Revolving Credit Facility (Textual) [Abstract]
Funded debt to EBITDA ratio	1.75
September 30, 2015 [Member]
Revolving Credit Facility (Textual) [Abstract]
Funded debt to EBITDA ratio	1.5
Thereafter [Member]
Revolving Credit Facility (Textual) [Abstract]
Funded debt to EBITDA ratio	1.25
Maximum [Member] \| September 30, 2013 [Member]
Revolving Credit Facility (Textual) [Abstract]
Funded debt to EBITDA ratio	2.25
Minimum [Member]
Revolving Credit Facility (Textual) [Abstract]
Minimum fixed charge coverage ratio	1.25

Fixed charge measuring ratio measured quarterly on a rolling basis.

No definition available.

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- Definition

Funded debt to EBITDA ratio.

+ References

No definition available.

+ Details

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- Definition

Reduction in maximum borrowing capacity.

+ References

No definition available.

+ Details

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

- Definition

Prohibition for purchase money financing on incurring additional indebtedness without the prior approval of the bank.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Ratio of restricted and unrestricted cash and marketable securities to workers compensation and safety incentive liabilities measured quarterly basis.

+ References

No definition available.

+ Details

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- Details

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- Definition

The 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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Period Type:	instant

- Definition

Including current and noncurrent portions, aggregate carrying amount of long-term borrowings as of the balance sheet date before deducting unamortized discount or premiums (if any). May include notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, which had initial maturities beyond one year or beyond the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number APB14-1

-Paragraph 31

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 20

-Article 5

Reference 4: 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 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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Balance Type:	credit
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- Definition

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

+ Details

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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.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Definition

Description of the fees for amounts available, but unused under the credit facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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 210.5-02.19(b),22(b))

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

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

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Balance Type:	na
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- Definition

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

+ References

No definition available.

+ Details

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

- Definition

Date the credit facility terminates, in CCYY-MM-DD format.

+ 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

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

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Data Type:	xbrli:dateItemType
Balance Type:	na
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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.

+ References

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	credit
Period Type:	instant