Reinsurance (Narrative) (Details)	12 Months Ended
Dec. 31, 2019 USD ($) reinsurer	Dec. 31, 2018 USD ($)
Reinsurance [Line Items]
Reinsurance recoverables	$ 9,593,400,000	$ 9,166,000,000.0
Allowance for doubtful accounts	2,800,000	300,000
Additions or write-downs charged against the allowance	2,500,000	0
Invested assets held in trusts	534,400,000	553,500,000
Related to Business Dispositions
Reinsurance [Line Items]
Reinsurance recoverables	4,860,000,000
Largest Reinsurance Recoverable Balances
Reinsurance [Line Items]
Reinsurance recoverables	$ 4,460,000,000
Number of reinsurers \| reinsurer	4
Sun Life
Reinsurance [Line Items]
Reinsurance recoverables	$ 606,100,000	761,700,000
Hartford
Reinsurance [Line Items]
Reinsurance recoverables	511,200,000	525,700,000
John Hancock
Reinsurance [Line Items]
Reinsurance recoverables	$ 2,490,000,000	$ 2,340,000,000

Number of Reinsurers

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Amount of increase (decrease) in allowance for credit loss on reinsurance recoverable.

+ References

No definition available.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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The total amount of cash and securities held by third party trustees pursuant to terms of debt instruments or other agreements as of the date of each statement of financial position presented, which can be used by the trustee only to pay the noncurrent portion of specified obligations.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
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- Definition

Amount, after valuation allowance, recoverable under reinsurance contracts including premium paid 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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.(a),6)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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-Name Accounting Standards Codification
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
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Amount of valuation allowance for reinsurance recoverables. 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.

+ References

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