INVESTMENTS - Narrative (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Separate Account Investment [Line Items]
Investments available-for-sale book value	$ 532.4	$ 465.7
Government National Mortgage Association Certificates And Obligations Federal National Mortgage Association Certificates And Obligations And Federal Home Loan Mortgage Corporation Certificates And Obligations | Collateralized Mortgage Obligations
Fair Value, Separate Account Investment [Line Items]
Mortgage-backed securities	312.1
Government National Mortgage Association Certificates And Obligations Federal National Mortgage Association Certificates And Obligations And Federal Home Loan Mortgage Corporation Certificates And Obligations | Collateralized Mortgage Backed Securities
Fair Value, Separate Account Investment [Line Items]
Mortgage-backed securities	677.4
Government National Mortgage Association Certificates And Obligations Federal National Mortgage Association Certificates And Obligations And Federal Home Loan Mortgage Corporation Certificates And Obligations | SBA asset backed securities
Fair Value, Separate Account Investment [Line Items]
Mortgage-backed securities	$ 57.1