Liabilities for Outstanding Claims, Losses and Loss Adjustment Expenses (Schedule of Incurred Claims Development) (Details) $ in Millions	Dec. 31, 2023 USD ($) Claim	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Commercial Multiple Peril Line [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	$ 4,553.5
Cumulative Paid Losses and ALAE, Net of Reinsurance	3,229.3
Unallocated loss adjustment expense	23.3
Net reserves	1,419.5
Commercial Multiple Peril Line [Member] | Year 2016 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	401.3	$ 397.2	$ 396.7	$ 400.1	$ 400.0	$ 401.0	$ 402.5	$ 398.2
IBNR	$ 6.5
Cumulative Incurred Claim Count | Claim	14,426
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 374.3	365.4	347.7	331.8	306.8	261.9	215.2	128.7
Commercial Multiple Peril Line [Member] | Year 2017 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	494.8	493.6	494.0	491.5	487.5	481.1	473.9
IBNR	$ 13.4
Cumulative Incurred Claim Count | Claim	15,377
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 448.3	435.6	414.5	377.6	328.8	264.1	157.2
Commercial Multiple Peril Line [Member] | Year 2018 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	499.7	495.8	490.6	489.5	495.6	511.1
IBNR	$ 19.1
Cumulative Incurred Claim Count | Claim	15,861
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 429.5	403.6	362.9	326.4	274.1	165.7
Commercial Multiple Peril Line [Member] | Year 2019 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	540.2	542.6	533.1	527.0	520.2
IBNR	$ 30.5
Cumulative Incurred Claim Count | Claim	14,895
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 444.5	396.3	348.7	288.5	156.5
Commercial Multiple Peril Line [Member] | Year 2020 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	514.9	531.5	546.7	562.1
IBNR	$ 45.8
Cumulative Incurred Claim Count | Claim	12,989
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 401.0	364.2	318.6	200.8
Commercial Multiple Peril Line [Member] | Year 2021 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	655.1	658.7	673.5
IBNR	$ 73.3
Cumulative Incurred Claim Count | Claim	14,771
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 450.0	392.6	245.1
Commercial Multiple Peril Line [Member] | Year 2022 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	749.2	748.1
IBNR	$ 145.1
Cumulative Incurred Claim Count | Claim	13,903
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 441.2	198.2
Commercial Multiple Peril Line [Member] | Year 2023 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	698.3
IBNR	$ 266.5
Cumulative Incurred Claim Count | Claim	11,956
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 240.5
Commercial Multiple Peril Line [Member] | Years 2016 to 2023 [Member]
Claims Development [Line Items]
Total reserves for accident years	1,324.2
Commercial Multiple Peril Line [Member] | Years 2015 and Prior [Member]
Claims Development [Line Items]
Total reserves for accident years	72.0
Workers' Compensation Line [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	1,495.9
Cumulative Paid Losses and ALAE, Net of Reinsurance	1,007.8
Unallocated loss adjustment expense	19.0
Net reserves	597.6
Workers' Compensation Line [Member] | Year 2014 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	110.5	112.9	116.4	118.2	120.7	123.1	124.3	125.8	$ 138.0	$ 143.5
IBNR	$ 5.7
Cumulative Incurred Claim Count | Claim	8,818
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 98.9	98.5	97.6	96.2	93.7	89.8	85.0	75.3	58.5	25.7
Workers' Compensation Line [Member] | Year 2015 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	110.0	113.8	116.3	119.0	122.2	125.8	132.1	136.0	157.0
IBNR	$ 7.8
Cumulative Incurred Claim Count | Claim	8,921
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 94.0	93.2	91.2	89.1	86.2	81.8	72.2	55.0	24.2
Workers' Compensation Line [Member] | Year 2016 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	118.3	122.3	124.9	128.3	133.5	139.9	152.8	158.9
IBNR	$ 6.2
Cumulative Incurred Claim Count | Claim	12,836
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 103.5	102.1	100.1	97.2	93.3	84.4	67.0	29.2
Workers' Compensation Line [Member] | Year 2017 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	125.7	129.6	132.4	136.7	139.9	148.7	159.6
IBNR	$ 8.2
Cumulative Incurred Claim Count | Claim	13,443
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 106.2	102.6	99.0	92.7	82.0	63.7	28.5
Workers' Compensation Line [Member] | Year 2018 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	145.8	149.2	150.8	152.6	161.3	165.2
IBNR	$ 13.1
Cumulative Incurred Claim Count | Claim	15,037
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 117.8	112.0	104.2	91.7	72.0	32.2
Workers' Compensation Line [Member] | Year 2019 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	159.5	163.2	162.9	165.0	170.5
IBNR	$ 14.8
Cumulative Incurred Claim Count | Claim	15,451
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 124.5	116.2	102.4	75.7	30.4
Workers' Compensation Line [Member] | Year 2020 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	142.4	150.6	166.8	167.1
IBNR	$ 16.0
Cumulative Incurred Claim Count | Claim	12,116
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 102.9	91.8	71.4	28.8
Workers' Compensation Line [Member] | Year 2021 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	175.5	180.8	178.5
IBNR	$ 17.1
Cumulative Incurred Claim Count | Claim	14,510
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 109.4	85.3	40.6
Workers' Compensation Line [Member] | Year 2022 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	205.9	198.5
IBNR	$ 32.4
Cumulative Incurred Claim Count | Claim	15,056
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 101.8	41.4
Workers' Compensation Line [Member] | Year 2023 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	202.3
IBNR	$ 64.8
Cumulative Incurred Claim Count | Claim	13,204
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 48.8
Workers' Compensation Line [Member] | Years 2013 and Prior [Member]
Claims Development [Line Items]
Total reserves for accident years	90.5
Workers' Compensation Line [Member] | Years 2014 to 2023 [Member]
Claims Development [Line Items]
Total reserves for accident years	488.1
Commercial Automobile Line [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	1,161.8
Cumulative Paid Losses and ALAE, Net of Reinsurance	718.9
Unallocated loss adjustment expense	4.8
Net reserves	467.3
Commercial Automobile Line [Member] | Year 2017 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	176.8	176.0	175.6	169.4	164.3	155.6	146.3
IBNR	$ 1.4
Cumulative Incurred Claim Count | Claim	10,916
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 168.3	160.9	144.4	125.8	95.5	64.8	24.9
Commercial Automobile Line [Member] | Year 2018 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	178.2	176.1	171.5	162.9	157.6	170.1
IBNR	$ 6.2
Cumulative Incurred Claim Count | Claim	10,611
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 156.0	142.7	114.5	83.2	52.7	26.8
Commercial Automobile Line [Member] | Year 2019 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	181.4	174.6	169.7	167.9	161.0
IBNR	$ 12.9
Cumulative Incurred Claim Count | Claim	9,803
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 147.9	126.5	94.8	64.5	27.1
Commercial Automobile Line [Member] | Year 2020 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	134.5	140.2	141.5	153.2
IBNR	$ 17.4
Cumulative Incurred Claim Count | Claim	5,890
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 96.3	71.4	42.1	21.0
Commercial Automobile Line [Member] | Year 2017 to 2023 [Member]
Claims Development [Line Items]
Total reserves for accident years	442.9
Commercial Automobile Line [Member] | Year 2021 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	146.1	156.5	154.1
IBNR	$ 33.9
Cumulative Incurred Claim Count | Claim	6,134
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 73.7	45.2	17.7
Commercial Automobile Line [Member] | Year 2022 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	173.3	157.5
IBNR	$ 66.7
Cumulative Incurred Claim Count | Claim	6,021
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 53.0	18.9
Commercial Automobile Line [Member] | Year 2023 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	171.5
IBNR	$ 109.3
Cumulative Incurred Claim Count | Claim	5,550
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 23.7
Commercial Automobile Line [Member] | Years 2016 and Prior [Member]
Claims Development [Line Items]
Total reserves for accident years	19.6
Core - General Liability And Umbrella - Occurrence [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	632.8
Cumulative Paid Losses and ALAE, Net of Reinsurance	318.8
Unallocated loss adjustment expense	3.2
Net reserves	332.2
Core - General Liability And Umbrella - Occurrence [Member] | Year 2014 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	55.6	54.0	54.0	53.4	54.0	53.8	60.8	57.9	48.9	70.7
IBNR	$ 1.4
Cumulative Incurred Claim Count | Claim	1,448
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 51.1	48.4	47.4	46.0	45.5	38.2	30.3	17.2	7.9	$ 1.6
Core - General Liability And Umbrella - Occurrence [Member] | Year 2015 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	43.9	45.5	49.1	50.5	52.1	53.8	58.6	57.9	66.6
IBNR	$ 1.7
Cumulative Incurred Claim Count | Claim	1,305
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 40.2	40.7	38.3	37.3	32.6	25.5	14.1	7.5	$ 1.4
Core - General Liability And Umbrella - Occurrence [Member] | Year 2016 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	59.2	54.2	54.5	53.7	55.8	57.8	61.0	58.5
IBNR	$ 3.1
Cumulative Incurred Claim Count | Claim	1,207
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 52.0	38.7	34.4	31.7	25.3	14.8	7.3	$ 0.7
Core - General Liability And Umbrella - Occurrence [Member] | Year 2017 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	60.8	61.0	62.9	63.0	66.3	67.1	58.2
IBNR	$ 5.8
Cumulative Incurred Claim Count | Claim	1,030
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 46.8	42.6	33.9	27.1	19.3	9.0	2.3
Core - General Liability And Umbrella - Occurrence [Member] | Year 2018 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	65.0	63.2	63.3	60.3	61.1	58.8
IBNR	$ 11.9
Cumulative Incurred Claim Count | Claim	960
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 40.7	38.1	27.2	18.8	4.4	1.0
Core - General Liability And Umbrella - Occurrence [Member] | Year 2019 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	73.7	69.3	60.3	60.0	58.9
IBNR	$ 14.3
Cumulative Incurred Claim Count | Claim	851
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 38.2	28.2	16.5	8.7	4.3
Core - General Liability And Umbrella - Occurrence [Member] | Year 2020 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	52.1	53.4	58.9	56.2
IBNR	$ 20.1
Cumulative Incurred Claim Count | Claim	552
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 17.8	11.9	9.2	2.1
Core - General Liability And Umbrella - Occurrence [Member] | Year 2021 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	73.7	70.0	58.3
IBNR	$ 35.9
Cumulative Incurred Claim Count | Claim	497
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 17.3	6.6	1.5
Core - General Liability And Umbrella - Occurrence [Member] | Year 2022 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	76.6	63.3
IBNR	$ 47.6
Cumulative Incurred Claim Count | Claim	487
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 9.3	0.4
Core - General Liability And Umbrella - Occurrence [Member] | Year 2023 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	72.2
IBNR	$ 58.7
Cumulative Incurred Claim Count | Claim	397
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 5.4
Core - General Liability And Umbrella - Occurrence [Member] | Years 2013 and Prior [Member]
Claims Development [Line Items]
Total reserves for accident years	15.0
Core - General Liability And Umbrella - Occurrence [Member] | Years 2014 to 2023 [Member]
Claims Development [Line Items]
Total reserves for accident years	314.0
Specialty Property And Casualty [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	1,450.7
Cumulative Paid Losses and ALAE, Net of Reinsurance	950.2
Unallocated loss adjustment expense	20.3
Net reserves	565.4
Specialty Property And Casualty [Member] | Year 2017 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	198.1	199.1	195.6	193.9	190.1	185.3	189.6
IBNR	$ 7.1
Cumulative Incurred Claim Count | Claim	6,850
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 177.3	168.5	155.6	138.7	125.9	102.6	55.5
Specialty Property And Casualty [Member] | Year 2018 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	191.1	191.1	190.2	193.7	194.1	193.0
IBNR	$ 9.8
Cumulative Incurred Claim Count | Claim	6,399
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 170.4	158.6	140.3	124.9	107.9	56.0
Specialty Property And Casualty [Member] | Year 2019 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	236.8	237.1	225.7	209.4	212.2
IBNR	$ 18.4
Cumulative Incurred Claim Count | Claim	6,480
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 187.1	164.9	136.5	113.9	71.5
Specialty Property And Casualty [Member] | Year 2020 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	169.5	164.9	170.8	181.1
IBNR	$ 19.8
Cumulative Incurred Claim Count | Claim	5,235
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 121.9	101.2	84.0	40.4
Specialty Property And Casualty [Member] | Year 2017 to 2023 [Member]
Claims Development [Line Items]
Total reserves for accident years	500.5
Specialty Property And Casualty [Member] | Year 2021 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	210.2	213.9	202.9
IBNR	$ 41.7
Cumulative Incurred Claim Count | Claim	5,868
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 125.9	106.6	59.2
Specialty Property And Casualty [Member] | Year 2022 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	215.3	218.3
IBNR	$ 67.1
Cumulative Incurred Claim Count | Claim	5,487
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 106.5	60.7
Specialty Property And Casualty [Member] | Year 2023 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	229.7
IBNR	$ 116.2
Cumulative Incurred Claim Count | Claim	3,973
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 61.1
Specialty Property And Casualty [Member] | Years 2016 and Prior [Member]
Claims Development [Line Items]
Total reserves for accident years	44.6
Specialty General Liability Claims Made [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	915.7
Cumulative Paid Losses and ALAE, Net of Reinsurance	546.7
Unallocated loss adjustment expense	7.0
Net reserves	384.5
Specialty General Liability Claims Made [Member] | Year 2017 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	94.1	93.6	92.5	94.1	96.1	100.6	99.1
IBNR	$ 1.9
Cumulative Incurred Claim Count | Claim	1,047
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 89.3	86.3	81.0	74.8	65.5	40.9	$ 12.1
Specialty General Liability Claims Made [Member] | Year 2018 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	121.7	121.6	121.7	121.2	117.8	112.2
IBNR	$ 4.8
Cumulative Incurred Claim Count | Claim	1,170
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 112.0	102.9	93.6	78.9	50.3	14.4
Specialty General Liability Claims Made [Member] | Year 2019 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	126.7	127.6	125.6	119.5	119.8
IBNR	$ 7.1
Cumulative Incurred Claim Count | Claim	1,213
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 107.4	95.4	77.0	53.3	16.5
Specialty General Liability Claims Made [Member] | Year 2020 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	119.1	123.3	134.2	137.3
IBNR	$ 10.0
Cumulative Incurred Claim Count | Claim	1,295
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 89.4	75.0	50.6	16.8
Specialty General Liability Claims Made [Member] | Year 2017 to 2023 [Member]
Claims Development [Line Items]
Total reserves for accident years	369.0
Specialty General Liability Claims Made [Member] | Year 2021 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	134.6	144.8	148.2
IBNR	$ 32.3
Cumulative Incurred Claim Count | Claim	1,194
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 76.7	49.9	15.8
Specialty General Liability Claims Made [Member] | Year 2022 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	149.0	162.3
IBNR	$ 59.4
Cumulative Incurred Claim Count | Claim	1,234
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 54.0	18.1
Specialty General Liability Claims Made [Member] | Year 2023 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	170.5
IBNR	$ 98.8
Cumulative Incurred Claim Count | Claim	2,530
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 17.9
Specialty General Liability Claims Made [Member] | Years 2016 and Prior [Member]
Claims Development [Line Items]
Total reserves for accident years	8.5
Personal Automobile Lines [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	2,519.7
Cumulative Paid Losses and ALAE, Net of Reinsurance	1,781.3
Unallocated loss adjustment expense	17.1
Net reserves	799.5
Personal Automobile Lines [Member] | Year 2018 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	412.2	409.3	406.7	400.3	395.3	394.2
IBNR	$ 5.4
Cumulative Incurred Claim Count | Claim	43,182
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 397.9	382.8	353.1	307.4	237.2	$ 121.7
Personal Automobile Lines [Member] | Year 2019 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	443.5	438.9	436.1	431.8	431.2
IBNR	$ 7.2
Cumulative Incurred Claim Count | Claim	42,513
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 413.3	385.1	336.6	262.2	$ 131.0
Personal Automobile Lines [Member] | Year 2020 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	307.0	312.3	347.0	378.0
IBNR	$ 13.7
Cumulative Incurred Claim Count | Claim	26,449
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 267.6	231.8	179.2	95.9
Personal Automobile Lines [Member] | Year 2021 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	408.5	411.6	407.2
IBNR	$ 35.1
Cumulative Incurred Claim Count | Claim	30,591
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 304.4	225.9	106.4
Personal Automobile Lines [Member] | Year 2022 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	458.6	441.9
IBNR	$ 90.8
Cumulative Incurred Claim Count | Claim	33,237
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 255.0	117.2
Personal Automobile Lines [Member] | Year 2023 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	489.9
IBNR	$ 200.3
Cumulative Incurred Claim Count | Claim	32,736
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 143.1
Personal Automobile Lines [Member] | Years 2018 to 2023 [Member]
Claims Development [Line Items]
Total reserves for accident years	738.4
Personal Automobile Lines [Member] | Years 2017 and Prior [Member]
Claims Development [Line Items]
Total reserves for accident years	44.0
Homeowners [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	2,347.0
Cumulative Paid Losses and ALAE, Net of Reinsurance	1,991.3
Unallocated loss adjustment expense	6.1
Net reserves	375.7
Homeowners [Member] | Year 2020 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	427.7	424.9	423.3	418.8
IBNR	$ 3.0
Cumulative Incurred Claim Count | Claim	35,333
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 417.8	408.1	387.7	$ 281.5
Homeowners [Member] | Year 2021 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	487.9	489.9	461.4
IBNR	$ 5.1
Cumulative Incurred Claim Count | Claim	39,172
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 471.4	449.1	$ 306.9
Homeowners [Member] | Year 2022 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	557.0	548.5
IBNR	$ 10.6
Cumulative Incurred Claim Count | Claim	34,989
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 511.7	$ 324.1
Homeowners [Member] | Year 2023 [Member]
Claims Development [Line Items]
Incurred Losses and ALAE, Net of Reinsurance	874.4
IBNR	$ 185.1
Cumulative Incurred Claim Count | Claim	44,865
Cumulative Paid Losses and ALAE, Net of Reinsurance	$ 590.4
Homeowners [Member] | Years 2020 to 2023 [Member]
Claims Development [Line Items]
Total reserves for accident years	355.7
Homeowners [Member] | Years 2019 and Prior [Member]
Claims Development [Line Items]
Total reserves for accident years	$ 13.9