Income Taxes (Components of Income Before Taxes and of Income Tax Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes
U.S.	$ 12,688	$ 10,535	$ 10,408
Non U.S.	1,456	1,307	892
Income (loss) before income taxes	14,144	11,842	11,300
Federal
Current	(208)	109	(155)
Deferred	5,332	3,832	(3,755)
Total	5,124	3,941	(3,910)
State
Current	13	179	123
Deferred	1,175	164	(634)
Total	1,188	343	(511)
Foreign
Current	476	311	95
Total	476	311	95
Total
Current	281	599	63
Deferred	6,507	3,996	(4,389)
Total	6,788	4,595	(4,326)
Reconciliation of the federal income tax expense at the statutory rate to the effective income tax expense
Statutory federal income tax expense	4,809	4,027	3,842
State taxes, net of federal benefit	784	117	(338)
Foreign tax paid	476	101	95
Tax consequences of the sale of engines to WMES	(306)	(36)	(36)
Uncertain tax positions	(195)	(101)	160
Permanent differences-nondeductible executive compensation	1,117	768	732
ETI basis restoration			(8,728)
Permanent differences and other	103	(281)	(53)
Total	$ 6,788	$ 4,595	$ (4,326)
Reconciliation of the federal income tax expense
Statutory federal income tax expense (as a percent)	34.00%	34.00%	34.00%
State taxes, net of federal benefit (as a percent)	5.50%	1.00%	(3.00%)
Foreign tax paid (as a percent)	3.40%	0.90%	0.80%
Tax consequences of the sale of engines to WMES (as a percent)	(2.10%)	(0.30%)	(0.30%)
Uncertain tax positions (as a percent)	(1.40%)	(0.90%)	1.40%
Permanent differences-162(m) (as a percent)	7.90%	6.50%	6.50%
ETI basis restoration (as a percent)			(77.20%)
Permanent differences and other (as a percent)	0.70%	(2.40%)	(0.50%)
Effective income tax expense (benefit) (as a percent)	48.00%	38.80%	(38.30%)