SEGMENT AND RELATED INFORMATION - Reconciliation of Operating Income from Segments to Consolidated (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated
Total segment operating income	$ 180,735	$ 172,926	$ 156,367
Total cost of revenues	(882,643)	(574,151)	(569,527)
Amortization of customer and trade name intangibles	(44,849)	(21,662)	(21,445)
Interest expense	(23,298)	(1,013)	(2,027)
Other income, net	1,544	3,129	5,498
Income before income taxes	158,981	175,042	159,838
Acquired software
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated
Total cost of revenues	(45,601)	(31,962)	(30,642)
Operating segment and corporate non-segment
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated
Total segment operating income	$ 271,185	$ 226,550	$ 208,454