SELECTED QUARTERLY DATA (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended										12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015		Dec. 31, 2014		Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Selected quarterly financial data [Abstract]
Net sales	$ 135,246	$ 144,161	$ 145,658	$ 142,015	[1]	$ 148,650	[2]	$ 156,341	$ 99,439	$ 82,646	$ 567,080	$ 487,076	$ 349,189
Cost of sales	109,203	116,749	117,098	115,202	[1]	121,091	[2]	128,561	81,493	68,576	458,253	399,721	286,952
Net earnings	$ 2,895	$ 4,920	$ 6,062	5,320	[1]	1,774	[2]	$ 1,261	$ 3,065	$ 2,503	19,197	8,603	15,908
Measurement Period Adjustment [Member]
Selected quarterly financial data [Abstract]
Cost of sales				114,900		120,800
Net earnings				$ 5,600		$ 2,000
Class A [Member]
Selected quarterly financial data [Abstract]
Net earnings											$ 3,331	$ 1,492	$ 2,868
Net earnings per share [Abstract]
Common share - basic and diluted (in dollars per share)	$ 0.23	$ 0.39	$ 0.49	$ 0.43	[1]	$ 0.14	[2]	$ 0.10	$ 0.25	$ 0.20	$ 1.53	$ 0.69	$ 1.32
Class A [Member] | Measurement Period Adjustment [Member]
Net earnings per share [Abstract]
Common share - basic and diluted (in dollars per share)				0.45		0.16
Class B [Member]
Selected quarterly financial data [Abstract]
Net earnings											$ 15,866	$ 7,111	$ 13,040
Net earnings per share [Abstract]
Common share - basic and diluted (in dollars per share)	$ 0.25	$ 0.42	$ 0.52	0.45	[1]	0.15	[2]	$ 0.11	$ 0.27	$ 0.22	$ 1.64	$ 0.75	$ 1.41
Class B [Member] | Measurement Period Adjustment [Member]
Net earnings per share [Abstract]
Common share - basic and diluted (in dollars per share)				$ 0.48		$ 0.17

[1] Revised from 10-Q disclosures to reflect immaterial measurement period adjustments related to the 2014 Acquisitions. First quarter 10-Q reflected cost of sales of $114.9 million, net earnings of $5.6 million, earnings per Class A common share of $0.45 per share and earnings per Class B common share of $0.48 per share.

[2] Revised from the disclosure in the Annual Report on Form 10-K for the year ended December 31, 2014 to reflect immaterial measurement period adjustments related to the 2014 Acquisitions. The 2014 10-K reflected, for the fourth quarter of 2014, cost of sales of $120.8 million, net earnings of $2.0 million, earnings per Class A common share of $0.16 per share and earnings per Class B common share of $0.17 per share.