Business Segments - Segment Net Operating Income (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting Information [Line Items]
Segment Net Operating Income (Loss)	$ 105.0		$ (27.8)	$ 266.4	$ (97.7)
Less: Net Loss attributable to Noncontrolling Interest	(1.5)		(0.1)	(3.6)	(0.1)
Debt Extinguishment, Pension Settlement and Other Charges	(2.8)	$ (70.2)		(0.1)	(70.2)
Goodwill Impairment Charge	0.0		0.0	0.0	(49.6)
Net Income (Loss) attributable to Kemper Corporation	73.7		(146.3)	220.4	(323.5)
Operating Segments
Segment Reporting Information [Line Items]
Segment Net Operating Income (Loss)	118.6		(18.5)	301.8	(65.6)
Operating Segments | Specialty Property & Casualty Insurance
Segment Reporting Information [Line Items]
Segment Net Operating Income (Loss)	103.6		(33.2)	275.1	(102.4)
Operating Segments | Non-Core Operations
Segment Reporting Information [Line Items]
Segment Net Operating Income (Loss)	(17.4)		(7.3)	(25.8)	(19.5)
Operating Segments | Life Insurance
Segment Reporting Information [Line Items]
Segment Net Operating Income (Loss)	15.0		14.7	26.7	36.8
Corporate and Other
Segment Reporting Information [Line Items]
Segment Net Operating Income (Loss)	(15.1)		(9.4)	(39.0)	(32.2)
Segment Reconciling Items
Segment Reporting Information [Line Items]
Change in Fair Value of Equity and Convertible Securities	(1.8)		2.3	(0.1)	5.5
Net Realized Investment Gains (Losses)	0.9		(22.9)	7.3	(30.3)
Impairment Losses	(1.7)		(0.8)	(3.0)	0.1
Acquisition and Disposition Related Transaction, Integration, Restructuring and Other Costs	(9.1)		(34.3)	(24.3)	(80.6)
Debt Extinguishment, Pension Settlement and Other Charges	(2.2)		(55.5)	(0.1)	(55.5)
Goodwill Impairment Charge	$ 0.0		$ 0.0	$ 0.0	$ (45.5)