Investments in Associated Companies - Summarized Financial Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Manufacturing And Services [Member]
Equity Method Investment Summarized Financial Information Abstract
Current Assets	$ 37,683	$ 37,998
Non-current Assets	936	1,244
Current Liabilities	24,858	26,683
Non-current Liabilities	1,457	1,166
Equity Method Investment Summarized Financial Information Income Statement [Abstract]
Revenue	42,555	41,448	$ 40,282
Gross Profit	13,440	13,082	12,887
Income Before Income Taxes	2,900	2,289	(2,843)
Net Income	1,471	1,210	(3,631)
Captive Insurance Company [Member]
Equity Method Investment Summarized Financial Information Abstract
Total Assets	120,154	116,742
Total Liabilities	54,258	58,775
Equity Method Investment Summarized Financial Information Income Statement [Abstract]
Revenue	14,042	5,632	7,058
Income Before Income Taxes	11,705	5,622	8,407
Net Income	$ 7,788	$ 5,148	$ 6,334