LIABILITY FOR UNPAID CLAIMS - Summary of Incurred Claims (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Liability For Claims And Claims Adjustment Expense [Line Items]
Incurred claims	$ 3,749.4
2019
Liability For Claims And Claims Adjustment Expense [Line Items]
Incurred claims	394.5	$ 394.6	$ 394.9	$ 383.2
2020
Liability For Claims And Claims Adjustment Expense [Line Items]
Incurred claims	616.6	613.7	$ 604.9
2021
Liability For Claims And Claims Adjustment Expense [Line Items]
Incurred claims	1,093.2	$ 1,098.9
2022
Liability For Claims And Claims Adjustment Expense [Line Items]
Incurred claims	$ 1,645.1