Revolving Credit Facility and Long-Term Debt - Additional Information (Detail) (USD $)	3 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Line of Credit Facility [Line Items]
Line of credit facility commitment fee description	The Agreement also provides for an unused commitment fee of 0.35% per year on the average daily unused amount of the revolving credit facility, and a fee of 1.75% of the face amount of each letter of credit.
Maximum amount of capital expenditures in 2015	$ 5,000,000
Maximum amount of capital expenditures in 2016	4,000,000
Wells Fargo [Member]
Line of Credit Facility [Line Items]
Term loan payment due June 30, 2015	3,000,000
Term loan payment due September 30, 2015	7,000,000
Term loan payment due December 31, 2015	15,000,000
Term loan payment due June 30, 2016	5,000,000
Term loan payment due September 30, 2016	5,000,000
Minimum [Member]
Line of Credit Facility [Line Items]
Minimum fixed charge coverage ratio	1.5
Ratio of restricted and unrestricted cash and marketable securities to workers' compensation and safety incentive liabilities	1
Prohibition on incurring additional indebtedness without the prior approval of the Bank in purchase money financing	200,000
Maximum [Member]
Line of Credit Facility [Line Items]
Prohibition on incurring additional indebtedness without the prior approval of the Bank in purchase money financing	400,000
Cash dividend	$ 0.22
Term Loan [Member]
Line of Credit Facility [Line Items]
Outstanding balance on term loan and revolving credit facility	40,000,000	40,000,000
Term loan from Bank, Interest rate description	One month LIBOR plus 2.25%
LIBOR plus rate	2.25%
Term loan with principal bank	5,000,000	5,100,000
Payment of monthly installments of term loan	18,375
Term Loan [Member] \| Wells Fargo [Member]
Line of Credit Facility [Line Items]
Credit facility borrowing capacity	40,000,000
Term loan maturity date	Dec. 31, 2016
Term Loan [Member] \| London Interbank Offered Rate (LIBOR) [Member] \| Wells Fargo [Member]
Line of Credit Facility [Line Items]
Term loan from Bank, Interest rate description	One month LIBOR plus 4.0%
LIBOR plus rate	4.00%
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Outstanding balance on term loan and revolving credit facility	5,800,000
Unused commitment fee on unused amount	0.35%
Revolving Credit Facility [Member] \| Wells Fargo [Member]
Line of Credit Facility [Line Items]
Credit facility borrowing capacity	14,000,000
Revolving Credit Facility [Member] \| Daily Floating Rate [Member]
Line of Credit Facility [Line Items]
Term loan from Bank, Interest rate description	A daily floating rate of one month LIBOR plus 2%
LIBOR plus rate	2.00%
Revolving Credit Facility [Member] \| Fixed Rate [Member]
Line of Credit Facility [Line Items]
Term loan from Bank, Interest rate description	A fixed rate of LIBOR plus 2.0%
LIBOR plus rate	2.00%
Standby Letters of Credit [Member] \| Wells Fargo [Member]
Line of Credit Facility [Line Items]
Credit facility borrowing capacity	5,000,000
Cash-Secured Letters of Credit [Member]
Line of Credit Facility [Line Items]
Unused commitment fee on unused amount	1.75%
Cash-Secured Letters of Credit [Member] \| Wells Fargo [Member]
Line of Credit Facility [Line Items]
Credit facility borrowing capacity	114,300,000
Cash-Secured Letters of Credit [Member] \| Wells Fargo [Member] \| Certificate of Deposit [Member]
Line of Credit Facility [Line Items]
Credit facility borrowing capacity	$ 114,300,000

Debt Instrument Covenant Maximum Capital Expenditure Threshold Year One

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Debt Instrument Covenant Maximum Capital Expenditure Threshold Year Two

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Fixed Charges Coverage Ratio

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

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

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Term loan payment due in fourth quarter.

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Term loan payment due in second quarter.

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Term loan payment due in seven quarters.

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Term loan payment due in six quarters.

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Term loan payment due in third quarter.

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

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Amount of long-term debt before deduction of unamortized discount or premium. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, with initial maturities beyond one year or the normal operating cycle, if longer.

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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.

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Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

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- Definition

The per share amount of a dividend declared, but not paid, as of the financial reporting date.

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

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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.

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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 the required periodic payment applied to principal.

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Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

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