Short-Duration Insurance Contracts - Schedule of Reinsurance Reserve Balances (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Gross reserves, beginning of year	$ 569.2
Less: reinsurance recoverables	404.3
Incurred claims and claim expenses:
Total claims and claim expenses incurred	68.3	$ 72.8	$ 71.5
Claims and claim expense payments for claims occurring during:
Plus: reinsurance recoverables	395.0	404.3
Gross reserves, end of year	565.2	569.2
Property & Casualty
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Gross reserves, beginning of year	420.6	416.8	388.7
Less: reinsurance recoverables	100.8	104.0	100.8
Net reserves, beginning of year	319.8	312.8	287.9
Incurred claims and claim expenses:
Claims occurring in the current year	514.8	552.8	557.0
Increase (decrease) in estimated reserves for claims occurring in prior years	(18.8)	(11.8)	0.0
Total claims and claim expenses incurred	496.0	541.0	557.0
Claims and claim expense payments for claims occurring during:
Current year	340.4	368.1	353.1
Prior years	172.1	165.9	179.0
Total claims and claim expense payments	512.5	534.0	532.1
Net reserves, end of year	303.3	319.8	312.8
Plus: reinsurance recoverables	101.2	100.8	104.0
Gross reserves, end of year	404.5	420.6	416.8
Group benefits
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Gross reserves, beginning of year	104.9	116.6	121.6
Less: reinsurance recoverables	25.2	27.7	27.9
Net reserves, beginning of year	79.7	88.9	93.7
Incurred claims and claim expenses:
Claims occurring in the current year	69.7	66.3	73.6
Increase (decrease) in estimated reserves for claims occurring in prior years	(5.0)	(14.5)	(13.9)
Total claims and claim expenses incurred	64.7	51.8	59.7
Claims and claim expense payments for claims occurring during:
Current year	30.1	31.1	33.8
Prior years	27.6	29.9	30.7
Total claims and claim expense payments	57.7	61.0	64.5
Net reserves, end of year	86.7	79.7	88.9
Plus: reinsurance recoverables	26.5	25.2	27.7
Gross reserves, end of year	$ 113.2	$ 104.9	$ 116.6