Goodwill and Intangible Assets - Schedule of Future Amortization Expense (Details) $ in Millions	Dec. 31, 2023 USD ($)
Finite-Lived Intangible Assets [Line Items]
Definite-life intangible assets, amortization expense, 2020	$ 40.8
Definite-life intangible assets, amortization expense, 2021	34.3
Definite-life intangible assets, amortization expense, 2022	30.1
Definite-life intangible assets, amortization expense, 2023	24.5
Definite-life intangible assets, amortization expense, 2024	21.8
Agent Relationships
Finite-Lived Intangible Assets [Line Items]
Definite-life intangible assets, amortization expense, 2020	5.5
Definite-life intangible assets, amortization expense, 2021	4.9
Definite-life intangible assets, amortization expense, 2022	4.9
Definite-life intangible assets, amortization expense, 2023	4.9
Definite-life intangible assets, amortization expense, 2024	4.9
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Definite-life intangible assets, amortization expense, 2020	0.4
Definite-life intangible assets, amortization expense, 2021	0.4
Definite-life intangible assets, amortization expense, 2022	0.3
Definite-life intangible assets, amortization expense, 2023	0.2
Definite-life intangible assets, amortization expense, 2024	0.2
Internal Use Software
Finite-Lived Intangible Assets [Line Items]
Definite-life intangible assets, amortization expense, 2020	33.3
Definite-life intangible assets, amortization expense, 2021	27.4
Definite-life intangible assets, amortization expense, 2022	23.4
Definite-life intangible assets, amortization expense, 2023	17.9
Definite-life intangible assets, amortization expense, 2024	15.3
Life Insurance
Finite-Lived Intangible Assets [Line Items]
VOBA, amortization expense, 2020	1.6
VOBA, amortization expense, 2021	1.6
VOBA, amortization expense, 2022	1.5
VOBA, amortization expense, 2023	1.5
VOBA, amortization expense, 2024	$ 1.4

Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of amortization for present value of future profits of insurance contract acquired in business combination expected to be recognized during fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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