Debt and Capital Lease Obligations (Details)	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jan. 01, 2018	Dec. 31, 2014 USD ($)
Debt Instrument [Line Items]
Long-term debt and capital lease obligations	$ 33,298,000	$ 29,263,000
Less current portion	(699,000)	(1,317,000)
Long-term debt and capital lease obligations, net of current portion	32,599,000	27,946,000
Term Loan and Line of Credit [Abstract]
Long-term debt and capital lease obligations	$ 33,298,000	29,263,000
Variable marginal rate on debt	0.75%
Letters of credit outstanding	$ 0	0			$ 0
Promissory Notes Payable to Individual Lenders [Abstract]
Stated interest rate (in hundredths)	2.26%
Notes With Affiliated Party [Abstract]
Amount due to related party for note		0
Minimum
Term Loan and Line of Credit [Abstract]
Variable marginal rate on debt	0.75%
Maximum
Term Loan and Line of Credit [Abstract]
Variable marginal rate on debt	1.75%
Term loan
Debt Instrument [Line Items]
Long-term debt and capital lease obligations	$ 9,244,000	9,653,000
Maturities of Long-term Debt [Abstract]
2017	422,000
2018	442,000
2019	459,000
2020	477,000
2021	496,000
Thereafter	6,948,000
Long-term debt	9,244,000
Term Loan and Line of Credit [Abstract]
Term loan borrowing capacity	10,800,000
Long-term debt and capital lease obligations	$ 9,244,000	9,653,000
Funded debt ratio maximum	3.5
Fixed charge coverage ratio minimum	1.20
Term loan | Forecast
Term Loan and Line of Credit [Abstract]
Funded debt ratio maximum				3.0
Line of credit
Debt Instrument [Line Items]
Long-term debt and capital lease obligations	$ 22,199,000	17,975,000
Maturities of Long-term Debt [Abstract]
2017	0
2018	0
2019	22,199,000
2020	0
2021	0
Thereafter	0
Long-term debt	22,199,000
Term Loan and Line of Credit [Abstract]
Maximum borrowing capacity	40,000,000
Long-term debt and capital lease obligations	22,199,000	17,975,000
Required availability of line of credit required for acquisitions	5,000,000.0
Loan agreement fee	$ 37,000	$ 36,000	$ 24,000
Unused debt instrument commitment fee (in hundredths)	0.15%
Line of credit | Minimum
Term Loan and Line of Credit [Abstract]
Unused debt instrument commitment fee (in hundredths)	0.15%
Line of credit | Maximum
Term Loan and Line of Credit [Abstract]
Unused debt instrument commitment fee (in hundredths)	0.30%
Letter of credit
Term Loan and Line of Credit [Abstract]
Maximum borrowing capacity	$ 2,500,000.0
Letter of credit | Minimum
Term Loan and Line of Credit [Abstract]
Variable marginal rate on debt		0.75%	0.75%
Debt Instrument, Fee	0.0075
Letter of credit | Maximum
Term Loan and Line of Credit [Abstract]
Variable marginal rate on debt		1.75%	1.75%
Debt Instrument, Fee	0.0175
Capital lease obligations
Debt Instrument [Line Items]
Long-term debt and capital lease obligations	$ 1,855,000	$ 1,635,000
Maturities of Long-term Debt [Abstract]
2017	333,000
2018	529,000
2019	333,000
2020	266,000
2021	199,000
Thereafter	399,000
Amount representing interest	(204,000)
Long-term debt	2,059,000
Capital Lease Obligations	1,855,000
Term Loan and Line of Credit [Abstract]
Long-term debt and capital lease obligations	$ 1,855,000	$ 1,635,000