Unpaid Claims and Claim Expenses - Summary of Reinsurance Reserve Balances (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information
Beginning gross reserves			$ 425.9
Claims and claim expense payments for claims occurring during:
Ending gross reserves	$ 481.9		481.9
Benefits, claims and settlement expenses	173.6	$ 164.8	558.2	$ 446.2
Property & Casualty
Segment Reporting Information
Beginning gross reserves	378.4	368.4	362.4	372.2
Less: reinsurance recoverables	109.8	108.9	110.3	112.9
Net reserves, beginning of period	268.6	259.5	252.1	259.3
Incurred claims and claim expenses:
Claims occurring in the current period	120.3	132.5	372.8	345.4
Decrease in estimated reserves for claims occurring in prior periods	2.0	(3.0)	8.0	(7.2)
Total claims and claim expenses incurred	122.3	129.5	380.8	338.2
Claims and claim expense payments for claims occurring during:
Current period	102.8	96.8	221.1	210.3
Prior periods	29.7	26.4	153.4	121.4
Total claims and claim expense payments	132.5	123.2	374.5	331.7
Net reserves, end of period	258.4	265.8	258.4	265.8
Plus: reinsurance recoverables	109.0	109.6	109.0	109.6
Ending gross reserves	367.4	375.4	367.4	375.4
Life and Annuity Segments
Claims and claim expense payments for claims occurring during:
Net reserves, end of period	114.5	64.7	114.5	64.7
Benefits, claims and settlement expenses	$ 51.3	$ 35.3	$ 177.4	$ 108.0

The amount needed to reflect the estimated ultimate cost of settling claims relating to insured events that have occurred on or before the balance sheet date, whether or not reported to the insurer at that date.

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