Commitments (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 1996
Property Subject to or Available for Operating Lease [Line Items]
Term of lease	15 years
Capital leased property	$ 30,849,000	$ 25,170,000
Proceeds from assignment of purchase option under lease	1,669,000	0	0
Increase in capital leased property	5,700,000
Capital lease obligations	22,000,000
Increase in capital lease obligations	6,700,000
Net book value of capital asset	18,300,000
Capital Leases, Future Minimum Payments, Present Value of Net Minimum Payments, Fiscal Year Maturity [Abstract]
2015	1,838,000
2016	1,854,000
2017	1,900,000
2018	1,947,000
2019	1,995,000
Remainder	21,408,000
Total minimum obligations	30,942,000
Less amounts representing interest (ranging from 5.8% to 18.8%)	(9,435,000)
Net present value of minimum obligations	21,507,000
Less current portion	(772,000)	(657,000)
Long-term capital lease obligations at December 31, 2013	20,735,000	14,901,000
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2015	622,000
2016	410,000
2017	295,000
2018	289,000
2019	283,000
Remainder	1,248,000
Total minimum lease payments	3,147,000
Rent expense charged to operations	1,100,000	1,100,000	1,100,000
Movement in Standard and Extended Product Warranty, Increase (Decrease) [Roll Forward]
Balance Beginning of Year	113,000	226,000	953,000
Accruals	140,000	70,000	(393,000)
Warranty Expenses	(64,000)	(183,000)	(334,000)
Balance End of Year	189,000	113,000	226,000
Capital Lease Obligations [Member]
Property Subject to or Available for Operating Lease [Line Items]
Proceeds from assignment of purchase option under lease	1,700,000
Capital Leases, Future Minimum Payments, Present Value of Net Minimum Payments, Fiscal Year Maturity [Abstract]
Interest rate percentage, minimum (in hundredths)	5.00%
Interest rate percentage, maximum (in hundredths)	18.80%
Annual rent increase percentage	2.50%
Accumulated amortization for property and equipment under capital leases	13,200,000	12,100,000
Property [Member]
Capital Leases, Future Minimum Payments, Present Value of Net Minimum Payments, Fiscal Year Maturity [Abstract]
2015	1,808,000
2016	1,853,000
2017	1,899,000
2018	1,947,000
2019	1,995,000
Remainder	21,408,000
Total minimum obligations	30,910,000
Less amounts representing interest (ranging from 5.8% to 18.8%)	(9,435,000)
Net present value of minimum obligations	21,475,000
Less current portion	(742,000)
Long-term capital lease obligations at December 31, 2013	20,733,000
Property [Member] | Capital Lease Obligations [Member]
Property Subject to or Available for Operating Lease [Line Items]
Term of lease	13 years			20 years
Capital leased property				12,300,000
Increase in capital leased property	11,700,000
Capital lease obligations	15,500,000			12,300,000
Net book value of capital asset	13,100,000
Equipment [Member]
Capital Leases, Future Minimum Payments, Present Value of Net Minimum Payments, Fiscal Year Maturity [Abstract]
2015	30,000
2016	1,000
2017	1,000
2018	0
2019	0
Remainder	0
Total minimum obligations	32,000
Less amounts representing interest (ranging from 5.8% to 18.8%)	0
Net present value of minimum obligations	32,000
Less current portion	(30,000)
Long-term capital lease obligations at December 31, 2013	$ 2,000