Reserves for Losses and Loss Adjustment Expenses - Summary of Information about Incurred and Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance (Detail) $ in Millions	Dec. 31, 2021 USD ($) claim	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Claims Development [Line Items]
Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance	$ 3,071.6
U.S. Operations | Liability
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	3,837.2
Cumulative Paid Losses & ALAE, Net of Reinsurance	2,355.9
Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance	59.4
Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance	1,540.7
U.S. Operations | Liability | Accident Year 2012
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	329.3	$ 328.2	$ 327.2	$ 328.9	$ 329.7	$ 335.9	$ 336.9	$ 339.3	$ 342.3	$ 329.9
Cumulative Paid Losses & ALAE, Net of Reinsurance	315.7	313.2	305.3	295.4	285.3	263.2	226.6	169.8	103.8	37.3
IBNR & Expected Development on Reported Claims	$ 35.6
Cumulative number of reported claims | claim	27,587
U.S. Operations | Liability | Accident Year 2013
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 357.3	344.8	343.1	346.6	351.5	360.4	361.0	355.8	344.5
Cumulative Paid Losses & ALAE, Net of Reinsurance	325.4	318.2	306.9	289.3	266.5	228.8	174.3	109.7	36.5
IBNR & Expected Development on Reported Claims	$ 48.4
Cumulative number of reported claims | claim	27,258
U.S. Operations | Liability | Accident Year 2014
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 341.3	327.4	321.9	323.9	326.3	330.0	337.1	328.6
Cumulative Paid Losses & ALAE, Net of Reinsurance	291.4	283.2	266.3	240.6	206.9	154.6	91.0	32.4
IBNR & Expected Development on Reported Claims	$ 56.3
Cumulative number of reported claims | claim	23,473
U.S. Operations | Liability | Accident Year 2015
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 347.9	335.4	328.0	328.7	330.3	343.8	339.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	289.3	263.9	236.4	195.6	140.2	86.9	33.7
IBNR & Expected Development on Reported Claims	$ 54.2
Cumulative number of reported claims | claim	21,729
U.S. Operations | Liability | Accident Year 2016
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 379.0	355.3	353.0	342.4	350.5	342.6
Cumulative Paid Losses & ALAE, Net of Reinsurance	293.8	255.6	217.1	144.1	84.5	28.5
IBNR & Expected Development on Reported Claims	$ 60.7
Cumulative number of reported claims | claim	18,693
U.S. Operations | Liability | Accident Year 2017
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 431.7	397.7	384.3	373.7	374.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	295.2	238.5	158.8	83.0	27.8
IBNR & Expected Development on Reported Claims	$ 102.3
Cumulative number of reported claims | claim	20,868
U.S. Operations | Liability | Accident Year 2018
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 420.4	414.5	430.4	426.1
Cumulative Paid Losses & ALAE, Net of Reinsurance	245.5	175.8	98.9	34.3
IBNR & Expected Development on Reported Claims	$ 117.0
Cumulative number of reported claims | claim	23,150
U.S. Operations | Liability | Accident Year 2019
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 427.1	423.7	421.1
Cumulative Paid Losses & ALAE, Net of Reinsurance	186.1	113.6	32.4
IBNR & Expected Development on Reported Claims	$ 181.8
Cumulative number of reported claims | claim	22,270
U.S. Operations | Liability | Accident Year 2020
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 386.7	404.2
Cumulative Paid Losses & ALAE, Net of Reinsurance	85.9	25.6
IBNR & Expected Development on Reported Claims	$ 261.2
Cumulative number of reported claims | claim	17,001
U.S. Operations | Liability | Accident Year 2021
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 416.5
Cumulative Paid Losses & ALAE, Net of Reinsurance	27.6
IBNR & Expected Development on Reported Claims	$ 366.6
Cumulative number of reported claims | claim	11,344
U.S. Operations | Professional
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 777.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	380.9
Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance	14.4
Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance	411.3
U.S. Operations | Professional | Accident Year 2012
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	24.3	24.4	24.7	24.9	24.5	24.0	25.8	28.6	28.3	27.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	24.3	24.0	24.2	23.5	22.6	21.4	19.9	16.9	8.6	2.3
IBNR & Expected Development on Reported Claims	$ 0.1
Cumulative number of reported claims | claim	642
U.S. Operations | Professional | Accident Year 2013
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 18.0	18.1	18.3	19.5	19.8	19.0	21.1	21.5	20.9
Cumulative Paid Losses & ALAE, Net of Reinsurance	17.9	17.9	17.9	17.5	17.6	14.2	10.9	6.3	1.9
IBNR & Expected Development on Reported Claims	$ 0.1
Cumulative number of reported claims | claim	625
U.S. Operations | Professional | Accident Year 2014
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 34.4	35.1	35.4	36.2	33.7	26.0	22.4	22.4
Cumulative Paid Losses & ALAE, Net of Reinsurance	33.6	33.3	32.3	25.5	24.1	15.1	5.4	2.3
IBNR & Expected Development on Reported Claims	$ 0.1
Cumulative number of reported claims | claim	1,044
U.S. Operations | Professional | Accident Year 2015
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 38.3	37.9	37.1	34.0	33.2	29.5	29.9
Cumulative Paid Losses & ALAE, Net of Reinsurance	31.7	31.3	26.2	20.8	15.6	8.3	1.8
IBNR & Expected Development on Reported Claims	$ 2.2
Cumulative number of reported claims | claim	1,831
U.S. Operations | Professional | Accident Year 2016
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 43.0	35.5	42.9	45.1	44.8	44.2
Cumulative Paid Losses & ALAE, Net of Reinsurance	34.4	30.8	28.9	24.6	11.9	2.4
IBNR & Expected Development on Reported Claims	$ (0.1)
Cumulative number of reported claims | claim	3,256
U.S. Operations | Professional | Accident Year 2017
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 99.5	87.9	78.3	61.8	60.1
Cumulative Paid Losses & ALAE, Net of Reinsurance	77.9	59.7	38.0	24.9	3.5
IBNR & Expected Development on Reported Claims	$ 4.2
Cumulative number of reported claims | claim	3,759
U.S. Operations | Professional | Accident Year 2018
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 94.8	79.2	73.2	70.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	62.6	43.8	16.7	4.5
IBNR & Expected Development on Reported Claims	$ (0.5)
Cumulative number of reported claims | claim	4,303
U.S. Operations | Professional | Accident Year 2019
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 105.0	96.8	94.4
Cumulative Paid Losses & ALAE, Net of Reinsurance	50.0	32.9	4.9
IBNR & Expected Development on Reported Claims	$ 22.5
Cumulative number of reported claims | claim	5,091
U.S. Operations | Professional | Accident Year 2020
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 142.6	152.6
Cumulative Paid Losses & ALAE, Net of Reinsurance	36.4	13.3
IBNR & Expected Development on Reported Claims	$ 78.7
Cumulative number of reported claims | claim	5,389
U.S. Operations | Professional | Accident Year 2021
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 177.9
Cumulative Paid Losses & ALAE, Net of Reinsurance	12.1
IBNR & Expected Development on Reported Claims	$ 149.2
Cumulative number of reported claims | claim	5,208
U.S. Operations | Specialty
Claims Development [Line Items]
Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance	$ 36.5
U.S. Operations | Property
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	911.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	841.9
Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance	(0.3)
Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance	68.8
U.S. Operations | Property | Accident Year 2012
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	97.4	98.6	98.6	98.7	98.7	98.5	98.8	98.7	101.8	103.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	97.4	98.6	98.6	98.7	98.4	98.4	98.2	98.0	97.2	70.1
IBNR & Expected Development on Reported Claims	$ 6.3
Cumulative number of reported claims | claim	15,005
U.S. Operations | Property | Accident Year 2013
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 77.2	78.2	78.4	78.2	77.8	78.2	78.7	79.9	74.5
Cumulative Paid Losses & ALAE, Net of Reinsurance	77.2	78.2	78.1	75.9	77.1	77.4	75.5	73.2	52.5
IBNR & Expected Development on Reported Claims	$ 0.9
Cumulative number of reported claims | claim	10,717
U.S. Operations | Property | Accident Year 2014
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 76.0	76.1	76.9	76.9	77.1	77.0	82.2	80.4
Cumulative Paid Losses & ALAE, Net of Reinsurance	76.0	76.1	76.4	76.3	76.4	75.7	73.1	51.6
IBNR & Expected Development on Reported Claims	$ 0.5
Cumulative number of reported claims | claim	8,559
U.S. Operations | Property | Accident Year 2015
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 69.2	69.2	69.1	68.9	69.9	73.4	74.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	69.0	68.5	68.3	67.9	68.6	67.6	44.6
IBNR & Expected Development on Reported Claims	$ 0.8
Cumulative number of reported claims | claim	7,746
U.S. Operations | Property | Accident Year 2016
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 56.5	56.6	56.6	57.1	57.6	59.4
Cumulative Paid Losses & ALAE, Net of Reinsurance	56.3	56.4	56.1	55.8	55.2	39.4
IBNR & Expected Development on Reported Claims	$ 2.0
Cumulative number of reported claims | claim	7,999
U.S. Operations | Property | Accident Year 2017
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 94.5	94.9	86.9	79.6	75.2
Cumulative Paid Losses & ALAE, Net of Reinsurance	88.4	100.8	113.9	95.3	54.4
IBNR & Expected Development on Reported Claims	$ 0.0
Cumulative number of reported claims | claim	10,388
U.S. Operations | Property | Accident Year 2018
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 96.9	95.1	93.1	89.2
Cumulative Paid Losses & ALAE, Net of Reinsurance	98.8	107.0	126.7	61.3
IBNR & Expected Development on Reported Claims	$ (12.9)
Cumulative number of reported claims | claim	11,145
U.S. Operations | Property | Accident Year 2019
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 98.4	88.8	91.4
Cumulative Paid Losses & ALAE, Net of Reinsurance	90.9	82.4	55.8
IBNR & Expected Development on Reported Claims	$ 2.1
Cumulative number of reported claims | claim	11,724
U.S. Operations | Property | Accident Year 2020
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 133.2	129.5
Cumulative Paid Losses & ALAE, Net of Reinsurance	116.6	75.9
IBNR & Expected Development on Reported Claims	$ (9.3)
Cumulative number of reported claims | claim	11,504
U.S. Operations | Property | Accident Year 2021
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 111.7
Cumulative Paid Losses & ALAE, Net of Reinsurance	71.3
IBNR & Expected Development on Reported Claims	$ (0.6)
Cumulative number of reported claims | claim	9,265
U.S. Operations | Specialty Admitted | Specialty
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 59.9
Cumulative Paid Losses & ALAE, Net of Reinsurance	24.0
Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance	0.6
Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance	36.5
U.S. Operations | Specialty Admitted | Specialty | Accident Year 2012
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	3.3	3.3	3.6	3.5	3.9	4.0	4.3	4.9	6.7	7.5
Cumulative Paid Losses & ALAE, Net of Reinsurance	3.4	3.4	3.4	3.3	3.4	3.3	3.3	3.3	3.3	3.6
IBNR & Expected Development on Reported Claims	$ 0.0
Cumulative number of reported claims | claim	121
U.S. Operations | Specialty Admitted | Specialty | Accident Year 2013
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 0.9	0.9	0.9	0.9	1.7	2.5	4.6	8.6	10.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.9	0.9	0.9	0.9	0.9	0.9	0.9	0.9	0.4
IBNR & Expected Development on Reported Claims	$ 0.1
Cumulative number of reported claims | claim	47
U.S. Operations | Specialty Admitted | Specialty | Accident Year 2014
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 4.1	4.6	4.6	4.8	6.0	8.9	13.1	13.1
Cumulative Paid Losses & ALAE, Net of Reinsurance	4.1	4.0	4.1	4.1	4.0	4.0	3.3	1.1
IBNR & Expected Development on Reported Claims	$ 0.0
Cumulative number of reported claims | claim	45
U.S. Operations | Specialty Admitted | Specialty | Accident Year 2015
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 0.3	0.5	1.2	5.5	9.5	14.3	14.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.3	0.3	0.3	0.3	0.2	0.1	0.2
IBNR & Expected Development on Reported Claims	$ 0.0
Cumulative number of reported claims | claim	24
U.S. Operations | Specialty Admitted | Specialty | Accident Year 2016
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 3.3	4.7	6.2	11.2	15.0	15.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	2.8	2.2	2.2	2.2	1.6	1.3
IBNR & Expected Development on Reported Claims	$ 0.9
Cumulative number of reported claims | claim	56
U.S. Operations | Specialty Admitted | Specialty | Accident Year 2017
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 0.7	0.9	7.6	16.2	16.2
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.2	0.1	0.0	0.1	0.3
IBNR & Expected Development on Reported Claims	$ 1.0
Cumulative number of reported claims | claim	106
U.S. Operations | Specialty Admitted | Specialty | Accident Year 2018
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 3.5	3.3	17.4	20.9
Cumulative Paid Losses & ALAE, Net of Reinsurance	1.2	1.7	0.7	0.0
IBNR & Expected Development on Reported Claims	$ 2.6
Cumulative number of reported claims | claim	142
U.S. Operations | Specialty Admitted | Specialty | Accident Year 2019
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 5.6	8.5	22.7
Cumulative Paid Losses & ALAE, Net of Reinsurance	3.2	0.7	0.7
IBNR & Expected Development on Reported Claims	$ 0.6
Cumulative number of reported claims | claim	233
U.S. Operations | Specialty Admitted | Specialty | Accident Year 2020
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 10.3	25.4
Cumulative Paid Losses & ALAE, Net of Reinsurance	7.6	0.3
IBNR & Expected Development on Reported Claims	$ 2.3
Cumulative number of reported claims | claim	409
U.S. Operations | Specialty Admitted | Specialty | Accident Year 2021
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 27.9
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.3
IBNR & Expected Development on Reported Claims	$ 26.5
Cumulative number of reported claims | claim	427
International Operations | Argo Insurance Bermuda- Liability | Liability
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 172.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	88.8
Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance	0.0
Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance	84.0
International Operations | Argo Insurance Bermuda- Liability | Liability | Accident Year 2012
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.6	0.6	0.6	0.0	1.7	4.4	5.6	7.4	7.4	7.4
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
IBNR & Expected Development on Reported Claims	$ 0.5
Cumulative number of reported claims | claim	1,392
International Operations | Argo Insurance Bermuda- Liability | Liability | Accident Year 2013
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 6.0	5.3	5.3	2.2	4.9	8.5	8.5	8.5	8.5
Cumulative Paid Losses & ALAE, Net of Reinsurance	2.4	2.4	2.3	2.3	2.3	0.0	0.0	0.0	0.0
IBNR & Expected Development on Reported Claims	$ 0.7
Cumulative number of reported claims | claim	1,200
International Operations | Argo Insurance Bermuda- Liability | Liability | Accident Year 2014
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 1.6	2.3	2.3	1.5	6.2	9.8	9.8	9.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	1.4	1.4	1.2	1.2	0.1	0.1	0.0	0.0
IBNR & Expected Development on Reported Claims	$ (0.4)
Cumulative number of reported claims | claim	1,350
International Operations | Argo Insurance Bermuda- Liability | Liability | Accident Year 2015
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 51.3	45.1	45.4	35.4	24.8	14.3	11.3
Cumulative Paid Losses & ALAE, Net of Reinsurance	38.9	34.8	26.6	20.3	16.1	0.0	0.0
IBNR & Expected Development on Reported Claims	$ 0.0
Cumulative number of reported claims | claim	1,613
International Operations | Argo Insurance Bermuda- Liability | Liability | Accident Year 2016
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 0.8	6.1	6.6	14.0	14.0	13.9
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.2	0.1	0.1	0.0	0.0	0.0
IBNR & Expected Development on Reported Claims	$ 0.5
Cumulative number of reported claims | claim	1,943
International Operations | Argo Insurance Bermuda- Liability | Liability | Accident Year 2017
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 37.3	30.3	26.9	17.3	17.1
Cumulative Paid Losses & ALAE, Net of Reinsurance	19.7	18.0	3.4	3.3	0.0
IBNR & Expected Development on Reported Claims	$ 10.4
Cumulative number of reported claims | claim	2,129
International Operations | Argo Insurance Bermuda- Liability | Liability | Accident Year 2018
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 24.2	26.6	32.1	8.9
Cumulative Paid Losses & ALAE, Net of Reinsurance	18.5	18.3	13.8	0.0
IBNR & Expected Development on Reported Claims	$ 5.2
Cumulative number of reported claims | claim	1,110
International Operations | Argo Insurance Bermuda- Liability | Liability | Accident Year 2019
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 13.8	13.6	13.3
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.7	0.1	0.0
IBNR & Expected Development on Reported Claims	$ 12.7
Cumulative number of reported claims | claim	1,168
International Operations | Argo Insurance Bermuda- Liability | Liability | Accident Year 2020
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 24.9	23.3
Cumulative Paid Losses & ALAE, Net of Reinsurance	7.0	0.8
IBNR & Expected Development on Reported Claims	$ 16.6
Cumulative number of reported claims | claim	1,267
International Operations | Argo Insurance Bermuda- Liability | Liability | Accident Year 2021
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 12.3
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0
IBNR & Expected Development on Reported Claims	$ 12.3
Cumulative number of reported claims | claim	1,053
International Operations | Syndicate 1200 | Liability
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 65.5
Cumulative Paid Losses & ALAE, Net of Reinsurance	13.0
Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance	3.7
Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance	56.2
International Operations | Syndicate 1200 | Liability | Accident Year 2012
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
IBNR & Expected Development on Reported Claims	0.0
International Operations | Syndicate 1200 | Liability | Accident Year 2013
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
IBNR & Expected Development on Reported Claims	0.0
International Operations | Syndicate 1200 | Liability | Accident Year 2014
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
IBNR & Expected Development on Reported Claims	0.0
International Operations | Syndicate 1200 | Liability | Accident Year 2015
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0
IBNR & Expected Development on Reported Claims	0.0
International Operations | Syndicate 1200 | Liability | Accident Year 2016
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0
IBNR & Expected Development on Reported Claims	0.0
International Operations | Syndicate 1200 | Liability | Accident Year 2017
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0
IBNR & Expected Development on Reported Claims	0.0
International Operations | Syndicate 1200 | Liability | Accident Year 2018
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	19.9	19.5	19.6	17.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	6.1	5.9	2.5	0.6
IBNR & Expected Development on Reported Claims	5.0
International Operations | Syndicate 1200 | Liability | Accident Year 2019
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	15.2	15.7	14.6
Cumulative Paid Losses & ALAE, Net of Reinsurance	5.2	4.6	1.4
IBNR & Expected Development on Reported Claims	5.3
International Operations | Syndicate 1200 | Liability | Accident Year 2020
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	14.6	15.2
Cumulative Paid Losses & ALAE, Net of Reinsurance	1.5	1.1
IBNR & Expected Development on Reported Claims	8.0
International Operations | Syndicate 1200 | Liability | Accident Year 2021
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	15.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.2
IBNR & Expected Development on Reported Claims	12.7
International Operations | Syndicate 1200 | Professional
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	85.6
Cumulative Paid Losses & ALAE, Net of Reinsurance	17.5
Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance	10.5
Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance	78.6
International Operations | Syndicate 1200 | Professional | Accident Year 2012
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
IBNR & Expected Development on Reported Claims	0.0
International Operations | Syndicate 1200 | Professional | Accident Year 2013
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
IBNR & Expected Development on Reported Claims	0.0
International Operations | Syndicate 1200 | Professional | Accident Year 2014
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
IBNR & Expected Development on Reported Claims	0.0
International Operations | Syndicate 1200 | Professional | Accident Year 2015
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0
IBNR & Expected Development on Reported Claims	0.0
International Operations | Syndicate 1200 | Professional | Accident Year 2016
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0
IBNR & Expected Development on Reported Claims	0.0
International Operations | Syndicate 1200 | Professional | Accident Year 2017
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0
IBNR & Expected Development on Reported Claims	0.0
International Operations | Syndicate 1200 | Professional | Accident Year 2018
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	15.5	15.3	14.4	13.7
Cumulative Paid Losses & ALAE, Net of Reinsurance	4.6	4.5	1.8	0.1
IBNR & Expected Development on Reported Claims	4.6
International Operations | Syndicate 1200 | Professional | Accident Year 2019
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	20.2	20.9	19.5
Cumulative Paid Losses & ALAE, Net of Reinsurance	9.1	8.7	2.7
IBNR & Expected Development on Reported Claims	7.1
International Operations | Syndicate 1200 | Professional | Accident Year 2020
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	25.0	25.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	3.1	2.2
IBNR & Expected Development on Reported Claims	12.0
International Operations | Syndicate 1200 | Professional | Accident Year 2021
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	24.9
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.7
IBNR & Expected Development on Reported Claims	20.0
International Operations | Syndicate 1200 | Specialty
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	314.3
Cumulative Paid Losses & ALAE, Net of Reinsurance	143.9
Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance	0.0
Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance	170.4
International Operations | Syndicate 1200 | Specialty | Accident Year 2012
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
IBNR & Expected Development on Reported Claims	0.0
International Operations | Syndicate 1200 | Specialty | Accident Year 2013
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
IBNR & Expected Development on Reported Claims	0.0
International Operations | Syndicate 1200 | Specialty | Accident Year 2014
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
IBNR & Expected Development on Reported Claims	0.0
International Operations | Syndicate 1200 | Specialty | Accident Year 2015
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0
IBNR & Expected Development on Reported Claims	0.0
International Operations | Syndicate 1200 | Specialty | Accident Year 2016
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0
IBNR & Expected Development on Reported Claims	0.0
International Operations | Syndicate 1200 | Specialty | Accident Year 2017
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0
IBNR & Expected Development on Reported Claims	0.0
International Operations | Syndicate 1200 | Specialty | Accident Year 2018
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	53.0	55.0	53.8	43.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	25.5	32.7	23.8	3.0
IBNR & Expected Development on Reported Claims	2.2
International Operations | Syndicate 1200 | Specialty | Accident Year 2019
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	80.5	84.0	66.5
Cumulative Paid Losses & ALAE, Net of Reinsurance	65.8	65.8	31.3
IBNR & Expected Development on Reported Claims	5.1
International Operations | Syndicate 1200 | Specialty | Accident Year 2020
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	108.2	109.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	42.9	27.7
IBNR & Expected Development on Reported Claims	19.8
International Operations | Syndicate 1200 | Specialty | Accident Year 2021
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	72.6
Cumulative Paid Losses & ALAE, Net of Reinsurance	9.7
IBNR & Expected Development on Reported Claims	37.8
International Operations | Syndicate 1200 | Property
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	234.6
Cumulative Paid Losses & ALAE, Net of Reinsurance	95.5
Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance	0.0
Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance	139.1
International Operations | Syndicate 1200 | Property | Accident Year 2012
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	$ 0.0
IBNR & Expected Development on Reported Claims	0.0
International Operations | Syndicate 1200 | Property | Accident Year 2013
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	$ 0.0
IBNR & Expected Development on Reported Claims	0.0
International Operations | Syndicate 1200 | Property | Accident Year 2014
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0	$ 0.0
IBNR & Expected Development on Reported Claims	0.0
International Operations | Syndicate 1200 | Property | Accident Year 2015
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0	$ 0.0
IBNR & Expected Development on Reported Claims	0.0
International Operations | Syndicate 1200 | Property | Accident Year 2016
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	0.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0	$ 0.0
IBNR & Expected Development on Reported Claims	0.0
International Operations | Syndicate 1200 | Property | Accident Year 2017
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	0.0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.0	0.0	0.0	0.0	$ 0.0
IBNR & Expected Development on Reported Claims	0.0
International Operations | Syndicate 1200 | Property | Accident Year 2018
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	22.1	21.7	21.8	19.7
Cumulative Paid Losses & ALAE, Net of Reinsurance	14.8	14.4	6.1	$ 1.5
IBNR & Expected Development on Reported Claims	0.2
International Operations | Syndicate 1200 | Property | Accident Year 2019
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	38.7	40.1	37.2
Cumulative Paid Losses & ALAE, Net of Reinsurance	36.0	31.9	$ 9.5
IBNR & Expected Development on Reported Claims	1.2
International Operations | Syndicate 1200 | Property | Accident Year 2020
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	60.3	62.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	29.1	$ 20.0
IBNR & Expected Development on Reported Claims	6.0
International Operations | Syndicate 1200 | Property | Accident Year 2021
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	113.5
Cumulative Paid Losses & ALAE, Net of Reinsurance	15.6
IBNR & Expected Development on Reported Claims	$ 68.1