SEGMENT INFORMATION - Segment Information Applicable to Reportable Operating Segments (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022 USD ($) segment	Jun. 30, 2021 USD ($) segment	Jun. 30, 2022 USD ($) segment	Jun. 30, 2021 USD ($) 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	$ 828,509	$ 704,161	$ 1,616,853	$ 1,341,053
Operating income (loss):
Operating income (loss)	34,770	23,764	64,905	37,884
Other expenses, net	15	14	11	7
Income before taxes	34,785	23,778	64,916	37,891
Depreciation and amortization:
Depreciation and amortization	2,989	3,053	5,980	6,218
Total assets:
Total assets	1,123,633	1,031,272	1,123,633	1,031,272	$ 1,083,383
Business Solutions
Net sales:
Net sales	328,351	267,258	648,794	513,592
Enterprise Solutions
Net sales:
Net sales	348,954	307,161	684,351	572,446
Public Sector Solutions
Net sales:
Net sales	151,204	129,742	283,708	255,015
Operating Segments | Business Solutions
Net sales:
Net sales	328,351	267,258	648,794	513,592
Operating income (loss):
Operating income (loss)	22,279	8,365	42,952	16,785
Depreciation and amortization:
Depreciation and amortization	168	159	335	318
Total assets:
Total assets	430,763	370,608	430,763	370,608
Operating Segments | Enterprise Solutions
Net sales:
Net sales	348,954	307,161	684,351	572,446
Operating income (loss):
Operating income (loss)	15,389	20,509	29,703	33,052
Depreciation and amortization:
Depreciation and amortization	501	612	1,035	1,328
Total assets:
Total assets	663,837	603,960	663,837	603,960
Operating Segments | Public Sector Solutions
Net sales:
Net sales	151,204	129,742	283,708	255,015
Operating income (loss):
Operating income (loss)	1,071	(2,116)	(55)	(4,869)
Depreciation and amortization:
Depreciation and amortization	20	10	39	24
Total assets:
Total assets	86,743	84,301	86,743	84,301
Headquarters/Other
Operating income (loss):
Operating income (loss)	(3,969)	(2,994)	(7,695)	(7,084)
Depreciation and amortization:
Depreciation and amortization	2,300	2,272	4,571	4,548
Total assets:
Assets net of intercompany balance eliminations	(57,710)	(27,597)	(57,710)	(27,597)
Intersegment Elimination
Total assets:
Total assets	$ (41,439)	$ (37,457)	$ (41,439)	$ (37,457)