Investments - Mortgage Loan Credit Monitoring (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Vintage year, Direct financing leases
2025		$ 44.6
2024		10.6
2023		2.1
2022		127.7
2021		48.7
Prior (prior period)		342.8
Direct financing leases, Total amortized cost		576.5
Reinsurance recoverable and deposit receivable	$ 18,113.6	19,003.3
Mortgage and other loans
Accrued interest receivable on direct financing leases	0.0	1.5
A- and above
Vintage year, Direct financing leases
2022		32.7
2021		11.7
Prior (prior period)		213.1
Direct financing leases, Total amortized cost		257.5
BBB+ thru BBB-
Vintage year, Direct financing leases
2024		10.6
2022		94.5
2021		22.0
Prior (prior period)		97.5
Direct financing leases, Total amortized cost		224.6
BB+ thru BB-
Vintage year, Direct financing leases
2023		2.1
2022		0.5
2021		5.6
Prior (prior period)		32.2
Direct financing leases, Total amortized cost		40.4
B+ and below
Vintage year, Direct financing leases
2025		44.6
2021		9.4
Direct financing leases, Total amortized cost		54.0
Commercial mortgage loans
Vintage year, Mortgage loans and Other loans
2026	1,267.4
2025	1,941.6	1,880.4
2024	1,402.4	1,569.5
2023	808.2	1,194.4
2022	1,054.1	1,467.6
2021		1,866.1
Prior (current period)	8,880.0
Prior (prior period)		8,540.1
Mortgage loans and Other loans, Total amortized cost	15,353.7	16,518.1
Mortgage and other loans
Accrued interest receivable	68.9	65.2
Commercial mortgage loans \| A- and above
Vintage year, Mortgage loans and Other loans
2026	883.6
2025	1,691.2	1,568.5
2024	1,123.4	1,315.6
2023	730.1	900.9
2022	942.7	1,079.7
2021		1,738.8
Prior (current period)	7,406.1
Prior (prior period)		6,878.7
Mortgage loans and Other loans, Total amortized cost	12,777.1	13,482.2
Commercial mortgage loans \| BBB+ thru BBB-
Vintage year, Mortgage loans and Other loans
2026	284.8
2025	152.3	200.9
2024	199.5	189.7
2023	24.9	151.6
2022	51.2	172.1
2021		116.2
Prior (current period)	1,056.4
Prior (prior period)		1,187.9
Mortgage loans and Other loans, Total amortized cost	1,769.1	2,018.4
Commercial mortgage loans \| BB+ thru BB-
Vintage year, Mortgage loans and Other loans
2026	99.0
2025	98.1	111.0
2024	79.5	64.2
2023	44.3	109.5
2022	60.2	215.8
2021		11.1
Prior (current period)	145.5
Prior (prior period)		120.7
Mortgage loans and Other loans, Total amortized cost	526.6	632.3
Commercial mortgage loans \| B+ and below
Vintage year, Mortgage loans and Other loans
2023	8.9	32.4
Prior (current period)	272.0
Prior (prior period)		352.8
Mortgage loans and Other loans, Total amortized cost	280.9	385.2
Residential mortgage loans
Vintage year, Mortgage loans and Other loans
2026 mortgage loans excluding portfolio layer method basis adjustments	1,253.1
2025 mortgage loans excluding portfolio layer method basis adjustments	1,228.3	1,304.3
2024 mortgage loans excluding portfolio layer method basis adjustments	280.4	367.6
2023 mortgage loans excluding portfolio layer method basis adjustments	271.5	386.6
2022 mortgage loans excluding portfolio layer method basis adjustments	895.4	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)	1,373.6
Total mortgage loans excluding portfolio layer method basis adjustments	5,302.3	4,697.9
Unallocated portfolio layer method basis adjustment	(19.9)	(3.7)
Mortgage loans and Other loans, Total amortized cost	5,282.4	4,694.2
Mortgage and other loans
Accrued interest receivable	29.0	20.0
Residential mortgage loans \| Performing
Vintage year, Mortgage loans and Other loans
2026	1,253.1
2025	1,227.8	1,304.3
2024	280.4	366.3
2023	265.1	381.3
2022	890.1	919.1
2021		1,137.6
Prior (current period)	1,364.1
Prior (prior period)		564.3
Mortgage loans and Other loans, Total amortized cost	5,280.6	4,672.9
Residential mortgage loans \| Non-performing
Vintage year, Mortgage loans and Other loans
2025	0.5
2024		1.3
2023	6.4	5.3
2022	5.3	8.1
2021		6.9
Prior (current period)	9.5
Prior (prior period)		3.4
Mortgage loans and Other loans, Total amortized cost	$ 21.7	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	$ 47.0	124.5
2024	21.0	32.0
2023	16.2	29.4
Mortgage loans and Other loans, Total amortized cost	84.2	185.9
Mortgage and other loans
Accrued interest receivable	1.1	1.4
Other loans \| Performing
Vintage year, Mortgage loans and Other loans
2025	43.8	123.1
2024	17.7	28.4
2023	15.1	27.9
Mortgage loans and Other loans, Total amortized cost	76.6	179.4
Other loans \| Non-performing
Vintage year, Mortgage loans and Other loans
2025	3.2	1.4
2024	3.3	3.6
2023	1.1	1.5
Mortgage loans and Other loans, Total amortized cost	$ 7.6	$ 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
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
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Amount of net investment in direct financing lease originated four years prior to current fiscal year.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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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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