SEGMENT REPORTING (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Segment Reporting Information [Line Items]
Sales	$ 290,097	$ 252,287
Operating income for reportable segments	35,349	29,619
Adjustment for [Abstract]
Amortization of intangibles	2,642	2,234
Corporate and other expense, net	10,003	7,480
Total operating income	22,704	19,905
Interest expense, net	1,627	829
Other expense (income), net	1	(15)
Income before income taxes	21,076	19,091
Service Centers [Member]
Segment Reporting Information [Line Items]
Sales	210,091	175,071
Operating income for reportable segments	25,047	18,553
IPS [Member]
Segment Reporting Information [Line Items]
Sales	41,523	39,435
Operating income for reportable segments	7,117	8,248
SCS [Member]
Segment Reporting Information [Line Items]
Sales	38,483	37,781
Operating income for reportable segments	$ 3,185	$ 2,818