Basis of Presentation and Significant Accounting Policies - Adjustments to Amortization Expense (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
(Decrease) increase to DAC amortization expense:
Total	$ 5.1	$ (1.5)	$ (2.1)
Life & Retirement
(Decrease) increase to DAC amortization expense:
Total	5.1	(1.5)	(2.1)
Supplemental & Group Benefits
(Decrease) increase to DAC amortization expense:
Total	$ 0.0	$ 0.0	$ 0.0

Amount of amortization expense (reversal of amortization expense) of deferred policy acquisition costs from a revision in estimated gross profit or estimated gross margin.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=35755530&loc=d3e11264-158415

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 30
-Section 35
-Paragraph 7
-URI https://asc.fasb.org/extlink&oid=124506905&loc=d3e10129-158409

Name:	us-gaap_DeferredPolicyAcquisitionCostAmortizationExpenseEffectOfAdjustmentsToEstimatedGrossProfitOrEstimatedGrossMargin
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration