Investments Investments - Debt Service and Fixed Charge Coverage Ratios (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Commercial mortgage loans
Loans and Leases Receivable Disclosure [Line Items]
Fair market value, trading	$ 163.6	$ 156.6
Delinquent amount of loans at end of period	65.8	48.4
Commercial mortgage loans \| Nonperforming loans
Loans and Leases Receivable Disclosure [Line Items]
Fair market value, trading	0.7
Commercial mortgage loans \| Less than 50 Percent
Loans and Leases Receivable Disclosure [Line Items]
Fair market value, trading	14.9	0.0
Commercial mortgage loans \| 50 to 60 Percent
Loans and Leases Receivable Disclosure [Line Items]
Fair market value, trading	39.3	80.5
Commercial mortgage loans \| 61 to 70 Percent
Loans and Leases Receivable Disclosure [Line Items]
Fair market value, trading	99.5	35.5
Commercial mortgage loans \| 71 to 80 Percent
Loans and Leases Receivable Disclosure [Line Items]
Fair market value, trading	9.9	40.6
Middle market loans
Loans and Leases Receivable Disclosure [Line Items]
Fair market value, trading	112.1	111.7
Middle market loans \| Less than 50 Percent
Loans and Leases Receivable Disclosure [Line Items]
Fair market value, trading	59.8	90.6
Middle market loans \| 50 to 60 Percent
Loans and Leases Receivable Disclosure [Line Items]
Fair market value, trading	11.0	21.1
Middle market loans \| 61 to 70 Percent
Loans and Leases Receivable Disclosure [Line Items]
Fair market value, trading	6.4	0.0
Middle market loans \| 80 to 100 Percent
Loans and Leases Receivable Disclosure [Line Items]
Fair market value, trading	17.2	0.0
Greater than 1.20x \| Commercial mortgage loans
Loans and Leases Receivable Disclosure [Line Items]
Fair market value, trading	82.2	94.6
Greater than 1.20x \| Middle market loans
Loans and Leases Receivable Disclosure [Line Items]
Fair market value, trading	73.6	68.4
1.00 - 1.20x \| Commercial mortgage loans
Loans and Leases Receivable Disclosure [Line Items]
Fair market value, trading	14.9	0.0
1.00 - 1.20x \| Middle market loans
Loans and Leases Receivable Disclosure [Line Items]
Fair market value, trading	0.0	25.5
Less than 1.00x \| Commercial mortgage loans
Loans and Leases Receivable Disclosure [Line Items]
Fair market value, trading	0.0	13.7
Less than 1.00x \| Middle market loans
Loans and Leases Receivable Disclosure [Line Items]
Fair market value, trading	38.5	17.8
Debt Service Coverage Ratio, excluding footnote values \| Commercial mortgage loans
Loans and Leases Receivable Disclosure [Line Items]
Fair market value, trading	$ 97.1	$ 108.3

This is the principal amount of loans (across all types of loans) that are overdue in payment by a set number of days.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (e)(4)
-URI http://asc.fasb.org/extlink&oid=118948506&loc=d3e107314-111719

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+ References

No definition available.

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Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.4)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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