GOODWILL AND OTHER INTANGIBLE ASSETS (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Goodwill [Roll Forward]
Beginning balance			$ 145,788,000
Acquired during the year			29,463,000
Adjustments to prior year estimates			2,007,000
Ending balance	177,258,000		177,258,000
Other Intangibles Assets [Roll Forward]
Balance at beginning of period			63,189,000
Acquired during the year			16,387,000
Adjustments to prior year estimates			(2,502,000)
Amortization	(3,145,000)	(2,556,000)	(5,787,000)	(4,790,000)
Balance at end of period	71,287,000		71,287,000
Total Goodwill and Intangible Assets [Roll Forward]
Beginning Balance			208,977,000
Acquired during the year			45,850,000
Adjustment to prior year estimates			(495,000)
Amortization	(3,145,000)	(2,556,000)	(5,787,000)	(4,790,000)
Ending Balance	248,545,000		248,545,000
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	108,774,000		108,774,000		94,888,000
Accumulated amortization	(37,487,000)		(37,487,000)		(31,699,000)
Carrying amount, net	71,287,000		71,287,000		63,189,000
Service Centers [Member]
Goodwill [Roll Forward]
Beginning balance					112,669,000
Ending balance	131,229,000		131,229,000		112,669,000
Innovative Pumping Solutions [Member]
Goodwill [Roll Forward]
Beginning balance					15,980,000
Ending balance	28,890,000		28,890,000		15,980,000
Supply Chain Services [Member]
Goodwill [Roll Forward]
Beginning balance					17,139,000
Ending balance	17,139,000		17,139,000		17,139,000
Vendor Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	2,496,000		2,496,000		2,496,000
Accumulated amortization	(1,143,000)		(1,143,000)		(1,081,000)
Carrying amount, net	1,353,000		1,353,000		1,415,000
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	104,437,000		104,437,000		90,851,000
Accumulated amortization	(35,586,000)		(35,586,000)		(30,010,000)
Carrying amount, net	68,851,000		68,851,000		60,841,000
Non-Compete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	1,841,000		1,841,000		1,541,000
Accumulated amortization	(758,000)		(758,000)		(608,000)
Carrying amount, net	1,083,000		1,083,000		933,000
Customer Lists [Member] | Intangible Assets Related to Jerzy Acquisition [Member]
Goodwill [Roll Forward]
Adjustments to prior year estimates			300
Customer Lists [Member] | Intangible Assets Related to HSE Acquisition [Member]
Total Goodwill and Intangible Assets [Roll Forward]
Adjustment to prior year estimates			$ 2,800