SEGMENT REPORTING (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Adjustment for [Abstract]
Amortization of intangibles			$ 9,223	$ 5,787
Operating income	28,399	23,265	50,560	45,969
Interest expense, net	3,176	1,689	6,573	3,316
Other expense (income), net	141	21	(9)	22
Income before income taxes	25,082	21,555	43,996	42,631
Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales	381,603	307,942	730,107	598,039
Operating income for reportable segments	44,865	34,626	81,964	69,975
Adjustment for [Abstract]
Operating income	28,399	23,265	50,560	45,969
Operating Segments [Member] | Service Centers [Member]
Segment Reporting Information [Line Items]
Sales	248,839	217,925	480,063	428,023
Operating income for reportable segments	25,486	23,376	49,911	48,420
Operating Segments [Member] | IPS [Member]
Segment Reporting Information [Line Items]
Sales	90,575	52,954	170,456	94,477
Operating income for reportable segments	15,800	8,090	25,350	15,208
Operating Segments [Member] | SCS [Member]
Segment Reporting Information [Line Items]
Sales	42,189	37,063	79,588	75,539
Operating income for reportable segments	3,579	3,160	6,703	6,347
Segment Reconciling Items [Member]
Adjustment for [Abstract]
Amortization of intangibles	4,653	3,145	9,223	5,787
Corporate and other expense, net	$ 11,813	$ 8,216	$ 22,181	$ 18,219