Deferred Costs, Capitalized, Prepaid, and Other Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023		Dec. 31, 2022		Dec. 31, 2021
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred Policy Acquisition Cost, Beginning Balance	$ 635.6	[1]	$ 688.0		$ 610.4
Capitalizations	563.3		691.5		772.6
Amortization Expense	(591.7)		(696.5)		(693.1)
Experience Adjustment	(15.6)		(8.7)		(1.9)
Deferred Policy Acquisition Cost, Gross	591.6		674.3		688.0
Deferred Policy Acquisition Cost, Ending Balance	591.6		635.6	[1]	688.0
Disposal Group, Held-for-sale, Not Discontinued Operations
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred Policy Acquisition Costs			38.7		0.0
Reserve National Insurance Company | Disposal Group, Held-for-sale, Not Discontinued Operations
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred Policy Acquisition Costs			38.7		0.0
Term Life Insurance
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Capitalizations	57.7		60.6		75.6
Amortization Expense	(19.9)		(28.0)		(35.7)
Experience Adjustment	(15.6)		(8.7)		(1.9)
Property and Casualty Insurance Reserves
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred Policy Acquisition Cost, Beginning Balance	231.1		268.7		229.1
Capitalizations	505.6		630.9		697.0
Amortization Expense	(571.8)		(668.5)		(657.4)
Experience Adjustment	0.0		0.0		0.0
Deferred Policy Acquisition Cost, Gross	164.9		231.1		268.7
Deferred Policy Acquisition Cost, Ending Balance	164.9		231.1		268.7
Life Insurance
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred Policy Acquisition Cost, Beginning Balance	404.5		419.3		381.3
Deferred Policy Acquisition Cost, Gross	426.7		443.2		419.3
Deferred Policy Acquisition Cost, Ending Balance	$ 426.7		$ 404.5		$ 419.3

[1] As of January 1, 2023, the Company adopted ASU 2018-12 using the modified retrospective method applied as of the transition date of January 1, 2021. Prior period amounts in the financial statements have been recast to reflect application of the new guidance. See Note 2 to the Consolidated Financial Statements for additional information.