Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions		3 Months Ended		6 Months Ended			9 Months Ended
		Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025		Jun. 30, 2024	Sep. 30, 2024
Statement of Cash Flows [Abstract]
Net Income		$ 69.8	$ 74.4	$ 166.8		$ 144.6
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities
Net Realized Investment Gains				(0.8)		(8.1)
Impairment Losses		3.6	0.1	3.3		1.6
Depreciation and Amortization of Property, Equipment, Software and Intangible Assets Acquired				25.5		27.7
Settlement Related to Defined Benefit Pension Plan				0.0		(2.7)
Change in Accumulated Undistributed Earnings of Equity Method Limited Liability Investments				(6.0)		(23.2)
Change in Fair Value of Equity and Convertible Securities		0.5	1.2	0.4		(2.2)
Receivables from Policyholders				(64.2)		(32.6)
Reinsurance Recoverables				1.8		4.1
Deferred Policy Acquisition Costs				(29.8)		(16.6)
Insurance Reserves				87.3		(80.7)
Unearned Premiums				84.2		5.1
Income Taxes				18.4		38.7
Other				(29.3)		(36.2)
Net Cash Provided by Operating Activities				269.6		65.9
Cash Flows from Investing Activities:
Proceeds from the Sales, Calls and Maturities of Fixed Maturities				525.4		629.2
Proceeds from the Sales or Paydowns of Investments:
Equity Securities				12.0		19.3
Mortgage Loans				53.5		71.9
Other Investments				12.6		8.6
Purchases of Investments:
Fixed Maturities				(668.8)		(578.4)
Equity Securities				(77.4)		(6.3)
Real Estate Investments				(1.0)		(0.6)
Mortgage Loans				(108.3)		(55.3)
Other Investments				28.1		30.2
Net Sales (Purchases) of Short-term Investments				650.6		(12.6)
Acquisition of Software and Long-lived Assets				(15.3)		(33.0)
Settlement Proceeds from Company-Owned Life Insurance				2.9		6.2
Other				3.3		13.8
Net Cash Provided by Investing Activities				361.4		32.6
Cash Flows from Financing Activities:
Repayment of Long-term Debt				(450.0)		0.0
Proceeds from Policyholder Contract Obligations				30.0		59.1
Repayment of Policyholder Contract Obligations				(26.7)		(70.7)
Proceeds from Shares Issued under Employee Stock Purchase Plan				1.8		2.0
Common Stock Repurchases				(32.5)		0.0
Dividends Paid				(41.0)		(39.8)
Other				(1.0)		(5.8)
Net Cash Used in Financing Activities				(519.4)		(55.2)
Net increase (decrease) in cash				111.6	[1]	43.3	$ 43.3	[1]
Cash, Beginning of Year	[1]			65.4		64.1	$ 64.1
Cash, End of Period	[1]	$ 177.0	$ 107.4	177.0		107.4
Cash (paid) received during the year for:
Interest				(27.1)		(27.3)
Taxes				(22.2)		5.1
Operating Leases				(9.7)		(11.2)
Non-Cash Activities:
Right-of-Use Assets Obtained in Exchange for New Operating Lease Liabilities				$ 16.6		$ 7.4

[1] 1Includes amounts attributable to Kemper Reciprocal reported as non-controlling interest.