Acquisitions - Summary of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Millions	Jan. 01, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Liabilities:
Goodwill		$ 54.3	$ 43.5	$ 43.5	$ 49.1
Madison National
Assets
Investments	$ 90.4
Cash and short-term investments	123.4
Reinsurance recoverable	356.0
Intangible assets	59.4	$ 56.5
Other assets	23.2
Liabilities:
Investment contract and policy reserves	274.5
Unpaid claims and claim expenses	48.2
Unearned premiums	1.5
Other policyholder funds	152.8
Other liabilities	15.9
Total identifiable net assets acquired	159.5
Goodwill	12.8
Purchase price	172.3
Goodwill expected to be deductible for tax purposes	$ 18.6
Madison National | Minimum
Liabilities:
Acquired finite-lived intangible assets, useful lives	1 year
Madison National | Maximum
Liabilities:
Acquired finite-lived intangible assets, useful lives	10 years