GOODWILL AND OTHER INTANGIBLE ASSETS, Goodwill balance by reportable segment (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Amount of aggregate goodwill	$ 197,211	$ 197,362
Service Centers [Member]
Goodwill [Line Items]
Amount of aggregate goodwill	164,093	164,244
Innovative Pumping Solutions [Member]
Goodwill [Line Items]
Amount of aggregate goodwill	15,980	15,980
Supply Chain Services [Member]
Goodwill [Line Items]
Amount of aggregate goodwill	$ 17,138	$ 17,138