INTANGIBLE ASSETS AND GOODWILL - Narrative (Details) - USD ($)		7 Months Ended	8 Months Ended	12 Months Ended
	Oct. 01, 2021	Dec. 31, 2019	Sep. 03, 2019	Dec. 31, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Goodwill				$ 455,206,000	$ 455,206,000
Impairment	$ 0			$ 0
Finite-lived intangible asset, useful life				9 years 1 month 17 days
Tradenames, Customer Relationships and Technology
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets		$ 7,800,000	$ 10,600,000	$ 23,400,000	23,400,000
Capitalized software development costs
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets		$ 700,000		1,500,000	400,000
Advisory Services
Finite-Lived Intangible Assets [Line Items]
Goodwill				37,900,000	37,900,000
Technology Enabled Solutions
Finite-Lived Intangible Assets [Line Items]
Goodwill				417,300,000	417,300,000
Advanced Plan Administration
Finite-Lived Intangible Assets [Line Items]
Goodwill				88,900,000
Supplemental Benefits Administration
Finite-Lived Intangible Assets [Line Items]
Goodwill				190,200,000	190,100,000
Value Based Analytics
Finite-Lived Intangible Assets [Line Items]
Goodwill				138,200,000
Advisory Services
Finite-Lived Intangible Assets [Line Items]
Goodwill				$ 37,900,000	$ 38,000,000