Fair Values of Financial Instruments Carrying Amounts and Estimated Fair value of Financial Instruments Not Measured at Fair Value (Details) - USD ($) $ in Millions		Mar. 31, 2026	Dec. 31, 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Mortgage Loans, Carrying Amount	[1]	$ 2,066.3	$ 2,109.5
Policy Loans		3,702.9	3,668.1
Long-term Debt		3,762.0	3,767.6
Other Liabilities		2,913.1	2,995.8
Liabilities, Fair Value Disclosure		261.0	269.7
Fair Value, Nonrecurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Mortgage Loans, Fair Value Disclosure		1,919.3	1,965.1
Mortgage Loans, Carrying Amount		2,066.3	2,109.5
Policy Loans, Fair Value Disclosure		3,761.7	3,739.5
Policy Loans		3,702.9	3,668.1
Miscellaneous Long-Term Investments, Fair Value Disclosure		42.7	40.9
Miscellaneous Long-Term Investments		42.7	40.9
Financial Instruments, Financial Assets Fair Value Disclosure		5,723.7	5,745.5
Total Financial Instrument Assets Not Carried at Fair Value		5,811.9	5,818.5
Liabilities Related to Investment Contracts, Fair Value Disclosure		106.5
Long-term Debt, Fair Value Disclosure		3,552.1	3,641.4
Long-term Debt		3,762.0	3,767.6
Other Liabilities, Carrying Value		585.6	644.0
Other Liabilities		585.6	644.0
Liabilities, Fair Value Disclosure		4,244.2	4,285.4
Total Financial Instrument Liabilities Not Carried at Fair Value		4,454.1	4,411.6
Fair Value, Inputs, Level 1 | Fair Value, Nonrecurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Mortgage Loans, Fair Value Disclosure		0.0	0.0
Policy Loans, Fair Value Disclosure		0.0	0.0
Miscellaneous Long-Term Investments, Fair Value Disclosure		0.0	0.0
Financial Instruments, Financial Assets Fair Value Disclosure		0.0	0.0
Liabilities Related to Investment Contracts, Fair Value Disclosure		0.0
Long-term Debt, Fair Value Disclosure		2,992.7	2,548.2
Other Liabilities		0.0	0.0
Liabilities, Fair Value Disclosure		2,992.7	2,548.2
Fair Value, Inputs, Level 2 | Fair Value, Nonrecurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Mortgage Loans, Fair Value Disclosure		1,919.3	1,965.1
Policy Loans, Fair Value Disclosure		0.0	0.0
Miscellaneous Long-Term Investments, Fair Value Disclosure		42.5	40.7
Financial Instruments, Financial Assets Fair Value Disclosure		1,961.8	2,005.8
Liabilities Related to Investment Contracts, Fair Value Disclosure		106.5
Long-term Debt, Fair Value Disclosure		559.4	1,093.2
Other Liabilities		585.6	644.0
Liabilities, Fair Value Disclosure		1,251.5	1,737.2
Fair Value, Inputs, Level 3 | Fair Value, Nonrecurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Mortgage Loans, Fair Value Disclosure		0.0	0.0
Policy Loans, Fair Value Disclosure		3,761.7	3,739.5
Miscellaneous Long-Term Investments, Fair Value Disclosure		0.2	0.2
Financial Instruments, Financial Assets Fair Value Disclosure		3,761.9	3,739.7
Liabilities Related to Investment Contracts, Fair Value Disclosure		0.0
Long-term Debt, Fair Value Disclosure		0.0	0.0
Other Liabilities		0.0	0.0
Liabilities, Fair Value Disclosure		$ 0.0	$ 0.0

[1] 1Loan-to-Value Ratio utilizes the most recent internal valuation of the property