GOODWILL AND OTHER INTANGIBLE ASSETS, NET - Summary of Changes in Carrying Amount of Goodwill by Operating Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Finite-Lived Intangible Assets [Line Items]
Gross	$ 2,415,448	$ 949,167	$ 903,904
Accumulated impairment	(83,987)	(83,987)	(83,987)
Goodwill [Roll Forward]
Beginning balance, Goodwill	865,180	819,917
Additions	1,472,652	45,254
Divestitures and other adjustments	(6,371)	9
Ending balance, Goodwill	2,331,461	865,180
Financial Services
Finite-Lived Intangible Assets [Line Items]
Gross	2,043,613	591,237	549,906
Accumulated impairment	(44,047)	(44,047)	(44,047)
Goodwill [Roll Forward]
Beginning balance, Goodwill	547,190	505,859
Additions	1,458,747	41,322
Divestitures and other adjustments	(6,371)	9
Ending balance, Goodwill	1,999,566	547,190
Benefits and Insurance Services
Finite-Lived Intangible Assets [Line Items]
Gross	337,962	324,057	320,125
Accumulated impairment	(7,733)	(7,733)	(7,733)
Goodwill [Roll Forward]
Beginning balance, Goodwill	316,324	312,392
Additions	13,905	3,932
Divestitures and other adjustments	0	0
Ending balance, Goodwill	330,229	316,324
National Practices
Finite-Lived Intangible Assets [Line Items]
Gross	33,873	33,873	33,873
Accumulated impairment	(32,207)	(32,207)	$ (32,207)
Goodwill [Roll Forward]
Beginning balance, Goodwill	1,666	1,666
Additions	0	0
Divestitures and other adjustments	0	0
Ending balance, Goodwill	$ 1,666	$ 1,666