SEGMENT INFORMATION - Segment Information Applicable to Reportable Operating Segments (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022 USD ($) segment	Sep. 30, 2021 USD ($) segment	Sep. 30, 2022 USD ($) segment	Sep. 30, 2021 USD ($) segment	Dec. 31, 2021 USD ($)
Segment Reporting Information
Number of reportable segments | segment	3	3	3	3
Number of operating segments | segment	3	3	3	3
Net sales:
Net sales	$ 775,692	$ 751,368	$ 2,392,545	$ 2,092,421
Operating income (loss):
Operating income (loss)	31,739	27,328	96,644	65,212
Other expenses, net	308		319	7
Income before taxes	32,047	27,328	96,963	65,219
Depreciation and amortization:
Depreciation and amortization	3,020	2,947	9,000	9,165
Total assets:
Total assets	1,134,125	1,013,926	1,134,125	1,013,926	$ 1,083,383
Business Solutions
Net sales:
Net sales	315,816	281,425	964,610	795,017
Enterprise Solutions
Net sales:
Net sales	305,510	309,722	989,861	882,168
Public Sector Solutions
Net sales:
Net sales	154,366	160,221	438,074	415,236
Operating Segments | Business Solutions
Net sales:
Net sales	315,816	281,425	964,610	795,017
Operating income (loss):
Operating income (loss)	19,278	12,774	62,230	29,559
Depreciation and amortization:
Depreciation and amortization	167	169	502	487
Total assets:
Total assets	451,872	375,557	451,872	375,557
Operating Segments | Enterprise Solutions
Net sales:
Net sales	305,510	309,722	989,861	882,168
Operating income (loss):
Operating income (loss)	12,401	19,151	42,103	52,203
Depreciation and amortization:
Depreciation and amortization	482	560	1,517	1,888
Total assets:
Total assets	647,592	603,173	647,592	603,173
Operating Segments | Public Sector Solutions
Net sales:
Net sales	154,366	160,221	438,074	415,236
Operating income (loss):
Operating income (loss)	4,211	619	4,156	(4,250)
Depreciation and amortization:
Depreciation and amortization	20	19	59	43
Total assets:
Total assets	113,820	91,227	113,820	91,227
Headquarters/Other
Operating income (loss):
Operating income (loss)	(4,151)	(5,216)	(11,845)	(12,300)
Depreciation and amortization:
Depreciation and amortization	2,351	2,199	6,922	6,747
Total assets:
Assets net of intercompany balance eliminations	(79,159)	(56,031)	(79,159)	(56,031)
Intersegment Elimination
Total assets:
Total assets	$ (62,154)	$ (39,209)	$ (62,154)	$ (39,209)