Contingencies, Guarantees, Indemnifications and Leases - Guarantees and Indemnifications (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Guaranty Funds
Undiscounted liability balance for guaranty fund assessments	$ 21.7	$ 22.2
Premium tax offsets	10.0	$ 10.4
Guarantees to third parties primarily related to former subsidiaries and joint ventures
Guarantees and Indemnifications
Maximum exposure under guarantees	118.0
Guarantees related to P-Caps contingent funding agreements
Guarantees and Indemnifications
Maximum exposure under guarantees	750.0
Lawsuit alleging breach of fiduciary duty related to PFIO
Loss contingencies - disclosures
Estimated losses accrued related to legal matters	$ 0.0

No definition available.

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- Definition

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=118943654&loc=d3e12069-110248

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- References

No definition available.

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- References

No definition available.

+ Details

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- Definition

The amount of insurance-related assessment liability that is expected to be recovered through a premium tax offset based on current laws applied to in-force policies.

+ References

+ Details

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- Definition

Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)
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-Name Accounting Standards Codification
-Topic 450
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-Paragraph 9
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118942415&loc=d3e14557-108349

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=118943654&loc=d3e12021-110248

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- Definition

The liability as of the balance sheet date representing required funding mandated by statute or regulatory authority that is related directly or indirectly to underwriting activities, including pools for self-insurance and excluding premium taxes and income taxes. The funds derived from the assessments generally enable a government guarantor to pay insurance claims in the event that the underwriting insurer is insolvent or otherwise unable to meet its payment obligations.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 405
-SubTopic 30
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6392405&loc=d3e24119-109301

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-Publisher FASB
-Name Accounting Standards Codification
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