INVESTMENTS - SUMMARY OF CARRYING VALUE AND ESTIMATED FAIR VALUE OF OUTSTANDING COMMERCIAL MORTGAGE LOANS AND UNDERLYING COLLATERAL (Details) $ in Millions	Mar. 31, 2026 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]
2026	$ 102.6
2025	419.8
2024	183.8
2023	275.0
2022	268.6
Prior	603.1
Total amortized cost	1,852.9
Commercial mortgage loans	1,752.6
Collateral	5,137.7
Commercial Portfolio Segment \| Less than 60%
Financing Receivable, Credit Quality Indicator [Line Items]
2026	102.6
2025	303.1
2024	168.8
2023	197.4
2022	140.4
Prior	545.4
Total amortized cost	1,457.7
Commercial mortgage loans	1,385.5
Collateral	4,580.5
Commercial Portfolio Segment \| 60% to less than 70%
Financing Receivable, Credit Quality Indicator [Line Items]
2026	0.0
2025	88.6
2024	15.0
2023	17.7
2022	37.4
Prior	25.7
Total amortized cost	184.4
Commercial mortgage loans	175.4
Collateral	279.8
Commercial Portfolio Segment \| 70% to less than 80%
Financing Receivable, Credit Quality Indicator [Line Items]
2026	0.0
2025	18.1
2024	0.0
2023	59.9
2022	77.4
Prior	22.4
Total amortized cost	177.8
Commercial mortgage loans	162.8
Collateral	238.7
Commercial Portfolio Segment \| 80% to less than 90%
Financing Receivable, Credit Quality Indicator [Line Items]
2026	0.0
2025	10.0
2024	0.0
2023	0.0
2022	13.4
Prior	0.0
Total amortized cost	23.4
Commercial mortgage loans	21.5
Collateral	29.0
Commercial Portfolio Segment \| 90% to less than 100%
Financing Receivable, Credit Quality Indicator [Line Items]
2026	0.0
2025	0.0
2024	0.0
2023	0.0
2022	0.0
Prior	9.6
Total amortized cost	9.6
Commercial mortgage loans	7.4
Collateral	$ 9.7

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