SEGMENT REPORTING - Financial Information of Company's Segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Total revenue	$ 1,480,832	$ 1,113,921	$ 1,005,266
Operating income for reportable segments, excluding adjustments	176,741	122,964	101,520
Identifiable assets at year end	981,380	821,242	752,147
Capital expenditures	3,968	3,598	5,711
Depreciation	7,731	8,134	8,127
Amortization of intangibles	18,915	17,197	12,287
Service Centers
Segment Reporting Information [Line Items]
Total revenue	1,009,356	816,496	662,617
Operating income for reportable segments, excluding adjustments	127,174	98,931	71,834
Identifiable assets at year end	746,548	642,184	564,921
Capital expenditures	1,419	999	1,254
Depreciation	3,038	3,475	3,299
Amortization of intangibles	12,294	11,107	6,989
Innovative Pumping Solutions
Segment Reporting Information [Line Items]
Total revenue	231,102	139,591	187,991
Operating income for reportable segments, excluding adjustments	30,037	12,070	16,882
Identifiable assets at year end	144,352	134,374	130,505
Capital expenditures	2,506	2,574	4,457
Depreciation	4,549	4,270	4,441
Amortization of intangibles	6,621	6,090	5,298
Supply Chain Services
Segment Reporting Information [Line Items]
Total revenue	240,374	157,834	154,658
Operating income for reportable segments, excluding adjustments	19,530	11,963	12,804
Identifiable assets at year end	90,480	44,684	56,721
Capital expenditures	43	25	0
Depreciation	144	389	387
Amortization of intangibles	$ 0	$ 0	$ 0