SEGMENT DISCLOSURES - Schedule of Disaggregation of Revenue by Source (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Disaggregation of Revenue [Line Items]
Revenue	$ 438,884	$ 410,539	$ 1,353,193	$ 1,263,647
Financial Services
Disaggregation of Revenue [Line Items]
Revenue	322,295	298,372	1,004,158	932,388
Benefits and Insurance Services
Disaggregation of Revenue [Line Items]
Revenue	104,040	100,287	309,867	296,179
National Practices
Disaggregation of Revenue [Line Items]
Revenue	12,549	11,880	39,168	35,080
Accounting, tax, advisory and consulting
Disaggregation of Revenue [Line Items]
Revenue	322,295	298,372	1,004,158	932,388
Accounting, tax, advisory and consulting | Financial Services
Disaggregation of Revenue [Line Items]
Revenue	322,295	298,372	1,004,158	932,388
Accounting, tax, advisory and consulting | Benefits and Insurance Services
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Accounting, tax, advisory and consulting | National Practices
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Core benefits and insurance services
Disaggregation of Revenue [Line Items]
Revenue	99,950	95,951	298,688	283,599
Core benefits and insurance services | Financial Services
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Core benefits and insurance services | Benefits and Insurance Services
Disaggregation of Revenue [Line Items]
Revenue	99,950	95,951	298,688	283,599
Core benefits and insurance services | National Practices
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Non-core benefits and insurance services
Disaggregation of Revenue [Line Items]
Revenue	4,090	4,336	11,179	12,580
Non-core benefits and insurance services | Financial Services
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Non-core benefits and insurance services | Benefits and Insurance Services
Disaggregation of Revenue [Line Items]
Revenue	4,090	4,336	11,179	12,580
Non-core benefits and insurance services | National Practices
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Managed networking, hardware services
Disaggregation of Revenue [Line Items]
Revenue	10,336	9,205	30,774	27,226
Managed networking, hardware services | Financial Services
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Managed networking, hardware services | Benefits and Insurance Services
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Managed networking, hardware services | National Practices
Disaggregation of Revenue [Line Items]
Revenue	10,336	9,205	30,774	27,226
National practices consulting
Disaggregation of Revenue [Line Items]
Revenue	2,213	2,675	8,394	7,854
National practices consulting | Financial Services
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
National practices consulting | Benefits and Insurance Services
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
National practices consulting | National Practices
Disaggregation of Revenue [Line Items]
Revenue	$ 2,213	$ 2,675	$ 8,394	$ 7,854