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Fair Values of Financial Instruments Fair Value, by Balance Sheet Groupings (Details) - USD ($) $ in Millions | Mar. 31, 2018 | Dec. 31, 2017
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Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] |  |
Mortgage Loans, Fair Value | $ 2,235.1 | $ 2,306.2
Mortgage Loans, Carrying Value | 2,200.8 | 2,213.2
Policy Loans, Fair Value | 3,666.0 | 3,677.5
Policy Loans, Carrying Value | 3,573.3 | 3,571.1
Other Long-term Investments |  |
Miscellaneous Long-Term Investments, Fair Value | 153.2 | 162.3
Miscellaneous Long-Term Investments, Carrying Value | 153.2 | 162.3
Total Financial Instruments Assets Not Carried at Fair Value | 6,054.3 | 6,146.0
Financial Instruments, Financial Assets Fair Value Disclosure, Carrying Value | 5,927.3 | 5,946.6
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] |  |
Long-term Debt, Fair Value | 2,961.6 | 3,048.7
Long-term Debt, Carrying Value | 2,721.9 | 2,738.4
Collateralized Financings [Abstract] |  |
Federal Home Loan Bank (FHLB) Funding Agreements, Fair Value | 350.0 | 350.0
Federal Home Loan Bank (FHLB) Funding Agreements, Carrying Value | 350.0 | 350.0
Other Liabilities, Unfunded Commitments | 3.7 | 3.7
Total Financial Liabilities, Fair Value | 3,315.3 | 3,402.4
Total Financial Liabilities, Carrying Value | 3,075.6 | 3,092.1
Fair Value, Inputs, Level 1 |  |
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] |  |
Mortgage Loans, Fair Value | 0.0 | 0.0
Policy Loans, Fair Value | 0.0 | 0.0
Other Long-term Investments |  |
Miscellaneous Long-Term Investments, Fair Value | 0.0 | 0.0
Total Financial Instruments Assets Not Carried at Fair Value | 0.0 | 0.0
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] |  |
Long-term Debt, Fair Value | 2,155.7 | 1,171.8
Collateralized Financings [Abstract] |  |
Federal Home Loan Bank (FHLB) Funding Agreements, Fair Value | 0.0 | 0.0
Other Liabilities, Unfunded Commitments | 0.0 | 0.0
Total Financial Liabilities, Fair Value | 2,155.7 | 1,171.8
Fair Value, Inputs, Level 2 |  |
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] |  |
Mortgage Loans, Fair Value | 2,235.1 | 2,306.2
Policy Loans, Fair Value | 0.0 | 0.0
Other Long-term Investments |  |
Miscellaneous Long-Term Investments, Fair Value | 34.1 | 34.1
Total Financial Instruments Assets Not Carried at Fair Value | 2,269.2 | 2,340.3
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] |  |
Long-term Debt, Fair Value | 805.9 | 1,876.9
Collateralized Financings [Abstract] |  |
Federal Home Loan Bank (FHLB) Funding Agreements, Fair Value | 350.0 | 350.0
Other Liabilities, Unfunded Commitments | 3.7 | 3.7
Total Financial Liabilities, Fair Value | 1,159.6 | 2,230.6
Fair Value, Inputs, Level 3 |  |
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] |  |
Mortgage Loans, Fair Value | 0.0 | 0.0
Policy Loans, Fair Value | 3,666.0 | 3,677.5
Other Long-term Investments |  |
Miscellaneous Long-Term Investments, Fair Value | 119.1 | 128.2
Total Financial Instruments Assets Not Carried at Fair Value | 3,785.1 | 3,805.7
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] |  |
Long-term Debt, Fair Value | 0.0 | 0.0
Collateralized Financings [Abstract] |  |
Federal Home Loan Bank (FHLB) Funding Agreements, Fair Value | 0.0 | 0.0
Other Liabilities, Unfunded Commitments | 0.0 | 0.0
Total Financial Liabilities, Fair Value | $ 0.0 | $ 0.0

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- Definition Fair value of financial and nonfinancial obligations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
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- Definition Amount before allowance of loans made to policy and contract holders using their life insurance contracts' cash value or separate accounts as collateral. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums over and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.1(e)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.7(a)(7)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
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- Definition Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -URI http://asc.fasb.org/subtopic&trid=2196772 + Details
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- Definition The balance represents the amount of loans that are secured by real estate mortgages, offset by the reserve to cover probable credit losses on the loan portfolio. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.1(c)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
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- Definition Amount of commitment or contingent commitments to qualified affordable housing project investments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 740 -Section 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=64813897&loc=SL49122993-202985 + Details
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