Unpaid Loss and Loss Adjustment Expense - Claims Development Information, Incurred Losses (Details) $ in Millions	Dec. 31, 2022 USD ($) claim segment	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Home and renters
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 265.3
IBNR	$ 31.6
Cumulative Number of Reported Claims | claim	167,086
Pet
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 38.1
IBNR	$ 0.7
Cumulative Number of Reported Claims | segment	561,509,000,000
Car
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 260.7
IBNR	$ 38.8
Cumulative Number of Reported Claims | segment	248,837
2016 | Home and renters
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 0.0	$ 0.0	$ 0.0	$ 0.0	$ 0.0	$ 0.0	$ 0.0
IBNR	$ 0.0
Cumulative Number of Reported Claims | segment	8
2016 | Car
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 2.0	1.9	1.8	1.7	1.7	2.0	$ 1.6
IBNR	$ 0.1
Cumulative Number of Reported Claims | segment	1,630
2017 | Home and renters
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 1.7	1.7	1.7	1.7	1.7	1.7
IBNR	$ 0.0
Cumulative Number of Reported Claims | claim	1,758
2017 | Car
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 32.5	32.3	31.4	30.2	30.0	$ 28.6
IBNR	$ 0.9
Cumulative Number of Reported Claims | segment	29,073
2018 | Home and renters
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 13.4	13.4	13.4	13.5	15.0
IBNR	$ 0.0
Cumulative Number of Reported Claims | claim	10,530
2018 | Car
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 33.9	31.8	31.9	29.7	$ 31.4
IBNR	$ 3.0
Cumulative Number of Reported Claims | segment	44,104
2019 | Home and renters
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 46.3	46.3	46.1	46.0
IBNR	$ 0.0
Cumulative Number of Reported Claims | claim	19,492
2019 | Car
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 24.6	23.2	24.0	$ 24.2
IBNR	$ 3.2
Cumulative Number of Reported Claims | segment	51,129
2020 | Home and renters
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 51.5	51.5	53.0
IBNR	$ 0.5
Cumulative Number of Reported Claims | claim	30,205
2020 | Pet
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 1.0	0.6	0.7
IBNR	$ 0.0
Cumulative Number of Reported Claims | segment	20,796,000,000
2020 | Car
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 11.8	12.0	$ 10.8
IBNR	$ 3.1
Cumulative Number of Reported Claims | segment	37,311
2021 | Home and renters
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 55.9	59.4
IBNR	$ 2.3
Cumulative Number of Reported Claims | claim	53,285
2021 | Pet
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 9.7	10.0
IBNR	$ 0.2
Cumulative Number of Reported Claims | segment	195,156,000,000
2021 | Car
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 75.3	$ 75.3
IBNR	$ 6.6
Cumulative Number of Reported Claims | segment	42,985
2022 | Home and renters
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 96.5
IBNR	$ 28.8
Cumulative Number of Reported Claims | claim	51,808
2022 | Pet
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 27.4
IBNR	$ 0.5
Cumulative Number of Reported Claims | segment	345,557,000,000
2022 | Car
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 80.6
IBNR	$ 21.9
Cumulative Number of Reported Claims | segment	42,605