INTANGIBLE ASSETS AND GOODWILL - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 482,623		$ 482,623		$ 455,206
Advanced Plan Administration
Finite-Lived Intangible Assets [Line Items]
Goodwill	88,900		88,900
Supplemental Benefits Administration
Finite-Lived Intangible Assets [Line Items]
Goodwill	190,200		190,200
Value Based Analytics
Finite-Lived Intangible Assets [Line Items]
Goodwill	138,200		138,200
HealthSmart
Finite-Lived Intangible Assets [Line Items]
Goodwill	27,400		27,400
Tradenames, Customer Relationships and Technology
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	6,100	$ 5,900	12,300	$ 11,700
Capitalized software development costs
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	1,000	$ 600	1,600	$ 800
Advisory Services
Finite-Lived Intangible Assets [Line Items]
Goodwill	37,900		37,900
Technology Enabled Solutions
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 444,700		$ 444,700