Net Income (Loss) Per Unrestricted Share - Reconciliation of Numerator and Denominator in Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Earnings Per Share [Abstract]
Net Income (Loss) attributable to Kemper Corporation	$ 317.8	$ (272.1)	$ (286.6)
Weighted-average Unrestricted Shares Outstanding (in shares)	64,179,500	64,025,600	63,825,500
Equity-based Compensation Equivalent Shares (in shares)	596,500	0	0
Weighted-average Unrestricted Shares and Equivalent Shares Outstanding Assuming Dilution (in shares)	64,776,000	64,025,600	63,825,500
Basic (in dollars per share)	$ 4.95	$ (4.25)	$ (4.50)
Diluted (in dollars per share)	$ 4.91	$ (4.25)	$ (4.50)