Unpaid Loss and Loss Adjustment Expense - Claims Development Information, Incurred Losses (Details) $ in Millions	Dec. 31, 2024 USD ($) claim segment	Dec. 31, 2023 USD ($)	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 ($)
Home and renters
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 557.2
IBNR	$ 55.8
Cumulative Number of Reported Claims | claim	296,326
Accident amount (less than)	$ 0.1	$ 0.1	$ 0.1	$ 0.1	$ 0.1	$ 0.1	$ 0.1	$ 0.1	$ 0.1
IBNR, net of reinsurance (less than)					0.1	0.1	0.1	0.1	0.1
Pet
Claims Development [Line Items]
Total incurred losses and ALAE, net	156.6
IBNR	$ 3.7
Cumulative Number of Reported Claims | claim	1,772,173
Car
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 439.8
IBNR	$ 40.2
Cumulative Number of Reported Claims | claim	319,248
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	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	$ 3.3	3.4	2.0	1.8	1.7	1.7	1.7	2.0	$ 1.6
IBNR	$ 0.0
Cumulative Number of Reported Claims | claim	1,628
2017 | Home and renters
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 1.6	1.7	1.7	1.7	1.7	1.7	1.7	1.7
IBNR	$ 0.0
Cumulative Number of Reported Claims | claim	1,759
2017 | Car
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 38.1	38.0	32.5	32.3	31.4	30.2	30.0	$ 28.6
IBNR	$ 0.0
Cumulative Number of Reported Claims | claim	29,056
2018 | Home and renters
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 13.4	13.4	13.4	13.4	13.4	13.5	15.0
IBNR	$ 0.0
Cumulative Number of Reported Claims | claim	10,534
2018 | Car
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 42.1	38.6	33.9	31.8	31.9	29.7	$ 31.4
IBNR	$ 0.2
Cumulative Number of Reported Claims | claim	44,103
2019 | Home and renters
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 46.2	46.1	46.3	46.3	46.1	46.0
IBNR	$ 0.0
Cumulative Number of Reported Claims | claim	19,507
2019 | Car
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 31.6	33.2	24.6	23.2	24.9	$ 24.2
IBNR	$ 0.6
Cumulative Number of Reported Claims | claim	51,136
2020 | Home and renters
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 52.4	52.4	51.5	51.5	53.0
IBNR	$ 0.0
Cumulative Number of Reported Claims | claim	30,349
2020 | Pet
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 0.7	0.6	1.0	0.6	0.7
IBNR	$ 0.0
Cumulative Number of Reported Claims | claim	20,873
2020 | Car
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 15.4	16.7	11.8	12.0	$ 10.8
IBNR	$ 1.0
Cumulative Number of Reported Claims | claim	37,324
2021 | Home and renters
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 58.6	58.4	55.9	59.4
IBNR	$ 0.2
Cumulative Number of Reported Claims | claim	53,497
2021 | Pet
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 9.5	9.5	9.7	10.0
IBNR	$ 0.0
Cumulative Number of Reported Claims | claim	196,787
2021 | Car
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 84.7	86.8	75.3	$ 75.3
IBNR	$ 3.0
Cumulative Number of Reported Claims | claim	43,113
2022 | Home and renters
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 93.8	92.6	96.5
IBNR	$ 1.7
Cumulative Number of Reported Claims | claim	55,977
2022 | Pet
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 25.2	25.3	27.4
IBNR	$ 0.0
Cumulative Number of Reported Claims | claim	375,659
2022 | Car
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 92.3	92.0	$ 83.1
IBNR	$ 8.3
Cumulative Number of Reported Claims | claim	46,776
2023 | Home and renters
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 136.5	143.2
IBNR	$ 8.2
Cumulative Number of Reported Claims | claim	60,623
2023 | Pet
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 48.9	51.9
IBNR	$ 0.0
Cumulative Number of Reported Claims | claim	510,045
2023 | Car
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 81.1	$ 79.1
IBNR	$ 10.0
Cumulative Number of Reported Claims | claim	39,118
2024 | Home and renters
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 154.7
IBNR	$ 45.7
Cumulative Number of Reported Claims | claim	64,072
2024 | Pet
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 72.3
IBNR	$ 3.7
Cumulative Number of Reported Claims | claim	668,809
2024 | Car
Claims Development [Line Items]
Total incurred losses and ALAE, net	$ 51.2
IBNR	$ 17.1
Cumulative Number of Reported Claims | claim	26,994