Reportable Segment Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Net sales
Total net sales	$ 491,697	$ 439,977	$ 1,335,838	$ 1,177,332
Income (Loss) from operations	34,929	33,830	88,249	79,138
Reconciling items to income before income taxes
Interest expense	(5,454)	(6,252)	(16,904)	(20,364)
Other, net	(610)	(605)	(1,626)	1,300
Income before income taxes	28,865	26,973	69,719	60,074
External customers
Net sales
Total net sales	491,697	439,977	1,335,838	1,177,332
Intersegment sales
Net sales
Total net sales	0	0	0	0
Corporate and Eliminations
Net sales
Total net sales	(37,292)	(31,660)	(108,466)	(94,677)
Income (Loss) from operations	(4,386)	(2,774)	(11,011)	(12,256)
Corporate and Eliminations | External customers
Net sales
Total net sales	0	0	0	0
Corporate and Eliminations | Intersegment sales
Net sales
Total net sales	(37,292)	(31,660)	(108,466)	(94,677)
Commercial Trailer Products
Net sales
Total net sales	351,644	293,510	914,747	757,420
Income (Loss) from operations	26,429	17,323	58,447	37,197
Commercial Trailer Products | External customers
Net sales
Total net sales	333,873	276,564	859,867	704,712
Commercial Trailer Products | Intersegment sales
Net sales
Total net sales	17,771	16,946	54,880	52,708
Diversified Products
Net sales
Total net sales	132,179	132,131	387,171	379,614
Income (Loss) from operations	12,027	18,538	37,623	51,320
Diversified Products | External customers
Net sales
Total net sales	112,860	117,990	334,281	338,937
Diversified Products | Intersegment sales
Net sales
Total net sales	19,319	14,141	52,890	40,677
Retail
Net sales
Total net sales	45,166	45,996	142,386	134,975
Income (Loss) from operations	859	743	3,190	2,877
Retail | External customers
Net sales
Total net sales	44,964	45,423	141,690	133,683
Retail | Intersegment sales
Net sales
Total net sales	$ 202	$ 573	$ 696	$ 1,292