Income Taxes - Reconciliation of Effective Tax Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Expected federal tax on income	$ 36.7	$ 33.5	$ 49.6
Add (deduct) tax effects of:
Tax-exempt interest	(3.9)	(4.2)	(4.2)
Dividend received deduction	(2.2)	(1.5)	(1.4)
Goodwill impairment	0.0	0.2	5.9
CARES Act net operating loss carryback	0.0	(2.8)	0.0
Employee share-based compensation	(1.3)	(0.5)	0.3
Compensation deduction limitation	1.5	0.7	0.7
Prior year adjustments	0.1	(0.2)	(0.7)
Other, net	1.2	1.1	1.8
Total income tax expense	$ 32.1	$ 26.3	$ 52.0