Inventories (Details) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Inventories
Raw materials	$ 19,870,000	$ 17,485,000
Work in process	18,572,000	20,410,000
Finished goods	2,185,000	2,257,000
Inventories, total	40,627,000	40,152,000
Inventory reserve	12,300,000	12,000,000
Excess and obsolete inventory	$ 211,000	$ 254,000