SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) (USD $)	3 Months Ended												12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013	Dec. 31, 2012		Sep. 30, 2012	Jun. 30, 2012		Mar. 31, 2012	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Selected quarterly financial data [Abstract]
Net sales	$ 91,016,000	$ 101,164,000	[1]	$ 93,981,000	[1]	$ 63,028,000	$ 71,752,000	[2]	$ 76,059,000	$ 73,222,000	[2]	$ 65,561,000	$ 349,189,000	[3]	$ 286,594,000	[3]	$ 295,121,000
Cost of sales	73,160,000	81,136,000	[1]	78,724,000	[1]	53,932,000	60,426,000	[2]	63,472,000	61,081,000	[2]	55,136,000	286,952,000	[3]	240,115,000	[3]	244,749,000
Net earnings	7,397,000	7,380,000	[1]	1,689,000	[1]	(558,000)	(2,432,000)	[2]	2,492,000	1,441,000	[2]	872,000	15,908,000	[3]	2,373,000	[3]	3,764,000
Earnings (loss) per share [Abstract]
Restructuring charges							3,100,000						1,387,000		5,245,000		314,000
Acquisition-related costs		500,000		700,000
Class A [Member]
Selected quarterly financial data [Abstract]
Net earnings													2,868,000		372,000		620,000
Earnings (loss) per share [Abstract]
Common share - basic and diluted (in dollars per share)	$ 0.61	$ 0.62	[1]	$ 0.14	[1]	$ (0.05)	$ (0.21)	[2]	$ 0.20	$ 0.11	[2]	$ 0.07	$ 1.32	[3]	$ 0.17	[3]	$ 0.28
Class B [Member]
Selected quarterly financial data [Abstract]
Net earnings													$ 13,040,000		$ 2,001,000		$ 3,144,000
Earnings (loss) per share [Abstract]
Common share - basic and diluted (in dollars per share)	$ 0.65	$ 0.65	[1]	$ 0.15	[1]	$ (0.05)	$ (0.21)	[2]	$ 0.21	$ 0.12	[2]	$ 0.08	$ 1.41	[3]	$ 0.21	[3]	$ 0.33

[1] The net earnings for the quarters ended June 30, 2013 and September 30, 2013 have been restated to include the effects of measurement period adjustments related to the acquisitions of TRP and Array. These measurement period adjustments reduced the previously-reported net earnings by $0.7 million and $0.5 million for the quarters ended June 30, 2013 and September 30, 2013, respectively, and primarily related to the step-up of inventory to fair value, and higher depreciation and amortization expense related to the appraised fair values of property, plant and equipment, and the various intangible assets as further described in Note 2.

[2] The net loss for the quarter ended December 31, 2012 includes $3.1 million of restructuring charges primarily related to severance charges and the write-down of assets associated with the closure of the Company’s Vinita, Oklahoma manufacturing facility.

[3] Quarterly amounts of earnings per share may not agree to the total for the year due to rounding.