Unpaid Claims and Claim Expenses - Summary of Reinsurance Reserve Balances (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Segment Reporting Information
Beginning gross reserves			$ 425.9
Claims and claim expense payments for claims occurring during:
Ending gross reserves	$ 490.5		490.5
Benefits, claims and settlement expenses	207.6	$ 147.1	384.6	$ 281.4
Property & Casualty
Segment Reporting Information
Beginning gross reserves	356.2	374.1	362.4	372.2
Less: reinsurance recoverables	108.0	112.5	110.3	112.9
Net reserves, beginning of period	248.2	261.6	252.1	259.3
Incurred claims and claim expenses:
Claims occurring in the current period	144.1	118.1	252.4	212.9
Decrease in estimated reserves for claims occurring in prior periods	6.0	(4.2)	6.0	(4.2)
Total claims and claim expenses incurred	150.1	113.9	258.4	208.7
Claims and claim expense payments for claims occurring during:
Current period	84.4	79.1	118.2	113.5
Prior periods	45.3	36.9	123.7	95.0
Total claims and claim expense payments	129.7	116.0	241.9	208.5
Net reserves, end of period	268.6	259.5	268.6	259.5
Plus: reinsurance recoverables	109.8	108.9	109.8	108.9
Ending gross reserves	378.4	368.4	378.4	368.4
Life and Annuity Segments
Claims and claim expense payments for claims occurring during:
Net reserves, end of period	112.1	65.2	112.1	65.2
Benefits, claims and settlement expenses	$ 57.5	$ 33.2	$ 126.2	$ 72.7

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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