Major Customers (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Revenue, Major Customer [Line Items]
Total sales	$ 43,591,000	$ 37,434,000	$ 130,790,000	$ 106,477,000
Total product sales	43,171,000	32,342,000	127,152,000	97,346,000
Total tooling sales	420,000	5,092,000	3,638,000	9,131,000
Navistar [Member]
Revenue, Major Customer [Line Items]
Total sales	13,129,000	11,501,000	39,799,000	36,308,000
Volvo [Member]
Revenue, Major Customer [Line Items]
Total sales	12,310,000	1,871,000	35,315,000	5,008,000
Paccar [Member]
Revenue, Major Customer [Line Items]
Total sales	9,842,000	16,887,000	26,802,000	40,948,000
Yamaha [Member]
Revenue, Major Customer [Line Items]
Total sales	3,315,000	2,115,000	12,543,000	9,029,000
Other Customers [Member]
Revenue, Major Customer [Line Items]
Total sales	4,995,000	5,060,000	16,331,000	15,184,000
Product Sales [Member] | Navistar [Member]
Revenue, Major Customer [Line Items]
Total sales	13,104,000	11,330,000	39,724,000	35,548,000
Product Sales [Member] | Volvo [Member]
Revenue, Major Customer [Line Items]
Total sales	12,020,000	1,817,000	33,877,000	4,377,000
Product Sales [Member] | Paccar [Member]
Revenue, Major Customer [Line Items]
Total sales	9,752,000	12,044,000	26,423,000	33,896,000
Product Sales [Member] | Yamaha [Member]
Revenue, Major Customer [Line Items]
Total sales	3,315,000	2,115,000	12,543,000	9,029,000
Product Sales [Member] | Other Customers [Member]
Revenue, Major Customer [Line Items]
Total sales	4,980,000	5,036,000	14,585,000	14,496,000
Tooling Sales [Member] | Navistar [Member]
Revenue, Major Customer [Line Items]
Total sales	25,000	171,000	75,000	760,000
Tooling Sales [Member] | Volvo [Member]
Revenue, Major Customer [Line Items]
Total sales	290,000	54,000	1,438,000	631,000
Tooling Sales [Member] | Paccar [Member]
Revenue, Major Customer [Line Items]
Total sales	90,000	4,843,000	379,000	7,052,000
Tooling Sales [Member] | Yamaha [Member]
Revenue, Major Customer [Line Items]
Total sales	0	0	0	0
Tooling Sales [Member] | Other Customers [Member]
Revenue, Major Customer [Line Items]
Total sales	$ 15,000	$ 24,000	$ 1,746,000	$ 688,000