Short-term and long-term debt - Additional Information (Detail)			3 Months Ended	12 Months Ended
	Apr. 08, 2016 USD ($)	Jul. 02, 2015	Sep. 30, 2013	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Feb. 15, 2013 USD ($)	Jun. 01, 2012 USD ($)
Credit facility maximum borrowing				$ 50,000,000		$ 40,000,000
Capital leased assets gross				249,000
Principal balance of this mortgage note				93,000	$ 260,000
Line of Credit Facility, Current Borrowing Capacity				44,000,000
Letters of Credit Outstanding, Amount				130,000
FifthAmendmen
Debt Instrument, Maturity Date	Jun. 30, 2020
Revolving Credit Facility
Credit facility maximum borrowing				$ 46,000,000		36,000,000
Revolving Credit Facility | Eurodollar
Fixed charge coverage ratio percentage		2.25%
Minimum
Fixed charge coverage ratio			1.00	1.00
Minimum | FifthAmendmen
Credit facility maximum borrowing	$ 40,000,000
Minimum | Revolving Credit Facility | FifthAmendmen
Credit facility maximum borrowing	36,000,000
Maximum
Fixed charge coverage ratio			1.10	1.10
Maximum | FifthAmendmen
Credit facility maximum borrowing	50,000,000
Maximum | Revolving Credit Facility | FifthAmendmen
Credit facility maximum borrowing	$ 46,000,000
Mortgage Note
Debt Instrument, Maturity Date				Jun. 30, 2020
Vehicle and Equipment Loans | Minimum
Credit facility effective rate of interest				0.00%
Vehicle and Equipment Loans | Maximum
Credit facility effective rate of interest				6.70%
Term Loan
Credit facility maximum borrowing						$ 4,000,000
Interest rate description under PNC facility				Interest charges with respect to loans are computed on the actual principal amount of loans outstanding during the month at a rate per annum equal to (A) with respect to Domestic Rate Loans (as defined in the PNC Facility), the sum of the Alternate Base Rate (as defined in the PNC Facility) plus one half of one percent (.50%) and (B) with respect to Eurodollar Rate Loans, the sum of the Eurodollar Rate plus two and one quarter of one percent (2.25%).
Term Loan | Eurodollar
Fixed charge coverage ratio percentage		2.25%
Term Loan | Revolving Credit Facility | Base Rate
Fixed charge coverage ratio percentage		0.50%
Busey Bank
Principal balance of this mortgage note				$ 93,000
Busey Bank | Mortgage Note
Credit facility maximum borrowing							$ 855,000
Credit facility effective rate of interest							4.00%
Line of Credit Facility, Expiration Date				Jun. 01, 2017