Revolving Credit Facility and Long-Term Debt - Additional Information (Detail) - Agreement [Member] - USD ($)	1 Months Ended	3 Months Ended
	Jun. 30, 2018	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jul. 01, 2018
Line of Credit Facility [Line Items]
Credit facility borrowing used					$ 5,900,000
Line of credit facility commitment fee description					The Agreement also provides for an unused commitment fee of 0.375% per year on the average daily unused amount of the revolving credit line, as well as a fee of 1.75% of the face amount of each letter of credit reserved under the line of credit and 0.95% on standalone, fully secured letters of credit.
Outstanding balance on term loan and revolving credit facility					$ 0	$ 0
Ratio of restricted and unrestricted cash and investments to workers' compensation and safety incentive liabilities					100.00%
Line of credit facility dividend restrictions					the Company may not declare or pay any dividend in excess of $0.25 per share in total each fiscal quarter, subject to increase by no more than 10% each year beginning June 30, 2019, compared to the prior fiscal year
Dividends, per share					$ 0.25
Dividend to be payable date					Jun. 30, 2019
Scenario Forecast [Member]
Line of Credit Facility [Line Items]
Ratio of restricted and unrestricted cash and investments to workers' compensation and safety incentive liabilities		100.00%	100.00%	100.00%
Minimum [Member]
Line of Credit Facility [Line Items]
EBITDA					$ 30,000,000
Minimum [Member] | Scenario Forecast [Member]
Line of Credit Facility [Line Items]
EBITDA		$ 30,000,000	$ 30,000,000	$ 30,000,000
Maximum [Member]
Line of Credit Facility [Line Items]
Prohibition on incurring additional indebtedness without the prior approval of the Bank in purchase money financing					$ 1,000,000
Percentage of dividend payable					10.00%
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Credit facility borrowing capacity							$ 28,000,000
Credit facility, expiration date					Jul. 01, 2020
Unused commitment fee on unused amount during period					0.375%
Revolving Credit Facility [Member] | Daily Floating Rate [Member]
Line of Credit Facility [Line Items]
Term loan from Bank, Interest rate description					the daily floating rate of one month LIBOR plus 1.75%
LIBOR plus rate					1.75%
Revolving Credit Facility [Member] | Fixed Rate [Member]
Line of Credit Facility [Line Items]
Term loan from Bank, Interest rate description					the fixed rate of LIBOR plus 1.75%
LIBOR plus rate					1.75%
Standby Letters of Credit [Member]
Line of Credit Facility [Line Items]
Credit facility borrowing capacity					$ 7,500,000		$ 7,500,000
Line of Credit [Member]
Line of Credit Facility [Line Items]
Unused commitment fee on unused amount					1.75%
Fully Secured Letter of Credit [Member]
Line of Credit Facility [Line Items]
Unused commitment fee on unused amount					0.95%
Chubb Letter of Credit [Member]
Line of Credit Facility [Line Items]
Credit facility borrowing capacity	$ 63,700,000
Credit facility, expiration date	Jul. 01, 2019
Percentage of initial fee under letter of credit					2.50%
Percentage of aggregate fee under letter of credit					95.00%
Percentage of annual fee under letter of credit					1.25%
Chubb Letter of Credit [Member] | Collateral Accounts [Member]
Line of Credit Facility [Line Items]
Percentage of deposit in collateral accounts					50.00%
Chubb Letter of Credit [Member] | Collateral Accounts [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Deposit in collateral accounts					$ 16,000,000
Term Loan [Member]
Line of Credit Facility [Line Items]
Term loan from Bank, Interest rate description					one month LIBOR plus 2.0%
Term loan with principal bank					$ 4,100,000	$ 4,200,000
Payment of monthly principal of term loan					$ 18,375
Term Loan [Member] | London Interbank Offered Rate (LIBOR) [Member]
Line of Credit Facility [Line Items]
LIBOR plus rate					2.00%