INVESTMENTS - SUMMARY OF CARRYING VALUE AND ESTIMATED FAIR VALUE OF OUTSTANDING COMMERCIAL MORTGAGE LOANS AND UNDERLYING COLLATERAL (Details) $ in Millions	Jun. 30, 2025 USD ($)
Less than 60% \| Maximum
Financing Receivable, Credit Quality Indicator [Line Items]
Loan to value ratio	60.00%
60% to less than 70% \| Maximum
Financing Receivable, Credit Quality Indicator [Line Items]
Loan to value ratio	70.00%
60% to less than 70% \| Minimum
Financing Receivable, Credit Quality Indicator [Line Items]
Loan to value ratio	60.00%
70% to less than 80% \| Maximum
Financing Receivable, Credit Quality Indicator [Line Items]
Loan to value ratio	80.00%
70% to less than 80% \| Minimum
Financing Receivable, Credit Quality Indicator [Line Items]
Loan to value ratio	70.00%
80% to less than 90% \| Maximum
Financing Receivable, Credit Quality Indicator [Line Items]
Loan to value ratio	90.00%
80% to less than 90% \| Minimum
Financing Receivable, Credit Quality Indicator [Line Items]
Loan to value ratio	80.00%
90% to less than 100% \| Maximum
Financing Receivable, Credit Quality Indicator [Line Items]
Loan to value ratio	100.00%
90% to less than 100% \| Minimum
Financing Receivable, Credit Quality Indicator [Line Items]
Loan to value ratio	90.00%
Commercial Portfolio Segment
Financing Receivable, Credit Quality Indicator [Line Items]
2025	$ 130.4
2024	184.6
2023	305.2
2022	279.3
2021	139.3
Prior	533.9
Total amortized cost	1,572.7
Commercial mortgage loans	1,462.7
Collateral	4,350.5
Commercial Portfolio Segment \| Less than 60%
Financing Receivable, Credit Quality Indicator [Line Items]
2025	73.3
2024	153.3
2023	179.7
2022	143.0
2021	119.5
Prior	469.0
Total amortized cost	1,137.8
Commercial mortgage loans	1,067.5
Collateral	3,741.1
Commercial Portfolio Segment \| 60% to less than 70%
Financing Receivable, Credit Quality Indicator [Line Items]
2025	38.8
2024	31.3
2023	60.1
2022	24.2
2021	12.0
Prior	25.5
Total amortized cost	191.9
Commercial mortgage loans	180.3
Collateral	293.9
Commercial Portfolio Segment \| 70% to less than 80%
Financing Receivable, Credit Quality Indicator [Line Items]
2025	18.3
2024	0.0
2023	65.4
2022	51.0
2021	0.0
Prior	37.6
Total amortized cost	172.3
Commercial mortgage loans	153.2
Collateral	232.4
Commercial Portfolio Segment \| 80% to less than 90%
Financing Receivable, Credit Quality Indicator [Line Items]
2025	0.0
2024	0.0
2023	0.0
2022	61.1
2021	0.0
Prior	0.0
Total amortized cost	61.1
Commercial mortgage loans	54.2
Collateral	73.3
Commercial Portfolio Segment \| 90% to less than 100%
Financing Receivable, Credit Quality Indicator [Line Items]
2025	0.0
2024	0.0
2023	0.0
2022	0.0
2021	7.8
Prior	1.8
Total amortized cost	9.6
Commercial mortgage loans	7.5
Collateral	$ 9.8

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