Investments - Mortgage Loan Credit Monitoring (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Vintage year, Direct financing leases
2025	$ 45.5	$ 44.6
2024	10.5	10.6
2023	2.1	2.1
2022	125.8	127.7
2021		48.7
Prior (prior period)		342.8
Prior (current period)	371.1
Direct financing leases, Total amortized cost	555.0	576.5
Reinsurance recoverable and deposit receivable	18,592.2	19,003.3
Mortgage and other loans
Accrued interest receivable on direct financing leases	1.8	1.5
A- and above
Vintage year, Direct financing leases
2024	3.9
2022	40.5	32.7
2021		11.7
Prior (prior period)		213.1
Prior (current period)	227.5
Direct financing leases, Total amortized cost	271.9	257.5
BBB+ thru BBB-
Vintage year, Direct financing leases
2024	5.9	10.6
2022	84.8	94.5
2021		22.0
Prior (prior period)		97.5
Prior (current period)	97.3
Direct financing leases, Total amortized cost	188.0	224.6
BB+ thru BB-
Vintage year, Direct financing leases
2024	0.7
2023	2.1	2.1
2022	0.5	0.5
2021		5.6
Prior (prior period)		32.2
Prior (current period)	36.1
Direct financing leases, Total amortized cost	39.4	40.4
B+ and below
Vintage year, Direct financing leases
2025	45.5	44.6
2021		9.4
Prior (current period)	10.2
Direct financing leases, Total amortized cost	55.7	54.0
Commercial mortgage loans
Vintage year, Mortgage loans and Other loans
2026	795.0
2025	1,935.6	1,880.4
2024	1,456.4	1,569.5
2023	893.3	1,194.4
2022	1,245.5	1,467.6
2021		1,866.1
Prior (current period)	9,774.4
Prior (prior period)		8,540.1
Mortgage loans and Other loans, Total amortized cost	16,100.2	16,518.1
Mortgage and other loans
Accrued interest receivable	69.0	65.2
Commercial mortgage loans \| A- and above
Vintage year, Mortgage loans and Other loans
2026	568.0
2025	1,640.8	1,568.5
2024	1,180.0	1,315.6
2023	815.0	900.9
2022	1,074.3	1,079.7
2021		1,738.8
Prior (current period)	8,220.4
Prior (prior period)		6,878.7
Mortgage loans and Other loans, Total amortized cost	13,498.5	13,482.2
Commercial mortgage loans \| BBB+ thru BBB-
Vintage year, Mortgage loans and Other loans
2026	139.0
2025	183.9	200.9
2024	200.7	189.7
2023	24.8	151.6
2022	69.0	172.1
2021		116.2
Prior (current period)	1,120.0
Prior (prior period)		1,187.9
Mortgage loans and Other loans, Total amortized cost	1,737.4	2,018.4
Commercial mortgage loans \| BB+ thru BB-
Vintage year, Mortgage loans and Other loans
2026	88.0
2025	110.9	111.0
2024	75.7	64.2
2023	44.6	109.5
2022	102.2	215.8
2021		11.1
Prior (current period)	199.7
Prior (prior period)		120.7
Mortgage loans and Other loans, Total amortized cost	621.1	632.3
Commercial mortgage loans \| B+ and below
Vintage year, Mortgage loans and Other loans
2023	8.9	32.4
Prior (current period)	234.3
Prior (prior period)		352.8
Mortgage loans and Other loans, Total amortized cost	243.2	385.2
Residential mortgage loans
Vintage year, Mortgage loans and Other loans
2026 mortgage loans excluding portfolio layer method basis adjustments	722.2
2025 mortgage loans excluding portfolio layer method basis adjustments	1,305.9	1,304.3
2024 mortgage loans excluding portfolio layer method basis adjustments	321.9	367.6
2023 mortgage loans excluding portfolio layer method basis adjustments	326.3	386.6
2022 mortgage loans excluding portfolio layer method basis adjustments	886.3	927.2
2021 mortgage loans excluding portfolio layer method basis adjustments		1,144.5
Prior mortgage loans excluding portfolio layer method basis adjustments (prior period)		567.7
Prior mortgage loans excluding portfolio layer method basis adjustments (current period)	1,620.9
Total mortgage loans excluding portfolio layer method basis adjustments	5,183.5	4,697.9
Unallocated portfolio layer method basis adjustment	(6.9)	(3.7)
Mortgage loans and Other loans, Total amortized cost	5,176.6	4,694.2
Mortgage and other loans
Accrued interest receivable	25.0	20.0
Residential mortgage loans \| Performing
Vintage year, Mortgage loans and Other loans
2026	722.2
2025	1,305.8	1,304.3
2024	321.3	366.3
2023	321.8	381.3
2022	878.9	919.1
2021		1,137.6
Prior (current period)	1,607.5
Prior (prior period)		564.3
Mortgage loans and Other loans, Total amortized cost	5,157.5	4,672.9
Residential mortgage loans \| Non-performing
Vintage year, Mortgage loans and Other loans
2025	0.1
2024	0.6	1.3
2023	4.5	5.3
2022	7.4	8.1
2021		6.9
Prior (current period)	13.4
Prior (prior period)		3.4
Mortgage loans and Other loans, Total amortized cost	$ 26.0	25.0
Mortgage and other loans
Mortgage loans, delinquent to be considered non-performing (in days)	90 days
Other loans
Vintage year, Mortgage loans and Other loans
2025	$ 66.0	124.5
2024	23.8	32.0
2023	19.8	29.4
Mortgage loans and Other loans, Total amortized cost	109.6	185.9
Mortgage and other loans
Accrued interest receivable	1.2	1.4
Other loans \| Performing
Vintage year, Mortgage loans and Other loans
2025	62.2	123.1
2024	17.8	28.4
2023	17.7	27.9
Mortgage loans and Other loans, Total amortized cost	97.7	179.4
Other loans \| Non-performing
Vintage year, Mortgage loans and Other loans
2025	3.8	1.4
2024	6.0	3.6
2023	2.1	1.5
Mortgage loans and Other loans, Total amortized cost	$ 11.9	$ 6.5

The numbers of days for which a mortgage loan has been delinquent such that it is considered non-performing.

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Carrying amount as of the balance sheet date of interest earned but not received on direct financing lease. Also called accrued interest or accrued interest receivable.

+ References

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Amount of net investment in direct financing lease originated five years prior to current fiscal year.

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Amount of net investment in direct financing lease originated six or more years prior to current fiscal year.

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Amortized cost excluding accrued interest, before allowance for credit loss, of financing receivable before portfolio layer method adjustment. Excludes net investment in lease.

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Amortized cost excluding accrued interest, before allowance for credit loss, of financing receivable of portfolio layer method adjustment. Excludes net investment in lease.

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Amortized cost excluding accrued interest, of financing receivable before portfolio layer method basis adjustment originated more than five years prior to current fiscal year. Excludes net investment in lease.

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Amortized cost excluding accrued interest, of financing receivable before portfolio layer method basis adjustment originated more than six years prior to current fiscal year. Excludes net investment in lease.

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Amortized cost excluding accrued interest, of financing receivable before portfolio layer method basis adjustment originated in current fiscal year. Excludes net investment in lease.

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Amortized cost excluding accrued interest, of financing receivable originated more than six years prior to current fiscal year. Excludes net investment in lease.

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Amortized cost excluding accrued interest of financing receivable before portfolio layer method basis adjustment originated four years prior to current fiscal year. Excludes net investment in lease.

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Amortized cost excluding accrued interest of financing receivable before portfolio layer method basis adjustment originated three years prior to current fiscal year. Excludes net investment in lease.

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Amortized cost excluding accrued interest of financing receivable before portfolio layer method basis adjustment originated five years prior to current fiscal year. Excludes net investment in lease.

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Amortized cost excluding accrued interest of financing receivable originated five years prior to current fiscal year. Excludes net investment in lease.

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Amortized cost excluding accrued interest of financing receivable before portfolio layer method basis adjustment originated two years prior to current fiscal year. Excludes net investment in lease.

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Amortized cost excluding accrued interest of financing receivable before portfolio layer method basis adjustment originated in fiscal year prior to current fiscal year. Excludes net investment in lease.

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Amount excluding accrued interest, before allowance for credit loss, of net investment in direct financing lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Amount of net investment in direct financing lease originated more than five years prior to current fiscal year.

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Amount of net investment in direct financing lease originated four years prior to current fiscal year.

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Amount of net investment in direct financing lease originated in fiscal year prior to current fiscal year.

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Amount of net investment in direct financing lease originated three years prior to current fiscal year.

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Amount of net investment in direct financing lease originated two years prior to current fiscal year.

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Amortized cost excluding accrued interest, before allowance for credit loss, of financing receivable. Excludes net investment in lease.

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Amortized cost excluding accrued interest, of financing receivable originated more than five years prior to current fiscal year. Excludes net investment in lease.

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Amortized cost excluding accrued interest, of financing receivable originated four years prior to current fiscal year. Excludes net investment in lease.

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Amortized cost excluding accrued interest, of financing receivable originated three years prior to current fiscal year. Excludes net investment in lease.

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Amortized cost excluding accrued interest, of financing receivable originated in current fiscal year. Excludes net investment in lease.

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Amortized cost excluding accrued interest, of financing receivable originated two years prior to current fiscal year. Excludes net investment in lease.

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Amortized cost excluding accrued interest of financing receivable originated in fiscal year prior to current fiscal year. Excludes net investment in lease.

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Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

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Amount before valuation allowance recoverable under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves.

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