Unpaid Loss and Loss Adjustment Expense - Claims Development Information, Paid Losses (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Claims Development [Line Items]
Total unpaid loss and ALAE reserves, net	$ 148.6
Ceded unpaid loss and LAE	149.5	$ 120.2	$ 124.6	$ 72.7
Gross unpaid loss and ALAE	298.1	262.3	256.2	97.9
Home and renters
Claims Development [Line Items]
Total paid losses and ALAE, net	473.3
Total unpaid loss and ALAE reserves, net	83.8
Ceded unpaid loss and LAE	109.3
Gross unpaid loss and ALAE	193.1
Cumulative paid loss and ALAE, net of reinsurance	0.1	0.1	0.1	0.1	$ 0.1	$ 0.1	$ 0.1	$ 0.1	$ 0.1
Pet
Claims Development [Line Items]
Total paid losses and ALAE, net	151.8
Total unpaid loss and ALAE reserves, net	4.8
Ceded unpaid loss and LAE	6.2
Gross unpaid loss and ALAE	11.0
Car
Claims Development [Line Items]
Total paid losses and ALAE, net	379.8
Total unpaid loss and ALAE reserves, net (2)	59.6
Ceded unpaid loss and ALAE	34.1
Total unpaid loss and ALAE reserves, net	60.0
Ceded unpaid loss and LAE	34.0
Gross unpaid loss and ALAE	93.7
Fair value adjustment on insurance contract intangible liability	1.6
2016 | Home and renters
Claims Development [Line Items]
Total paid losses and ALAE, net	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
2016 | Car
Claims Development [Line Items]
Total paid losses and ALAE, net	3.3	2.2	1.9	1.7	1.6	1.6	1.5	1.2	$ 0.2
2017 | Home and renters
Claims Development [Line Items]
Total paid losses and ALAE, net	1.7	1.7	1.7	1.7	1.7	1.7	1.7	1.6
2017 | Car
Claims Development [Line Items]
Total paid losses and ALAE, net	38.3	24.6	31.7	30.8	30.1	28.1	24.3	$ 17.3
2018 | Home and renters
Claims Development [Line Items]
Total paid losses and ALAE, net	13.4	13.4	13.4	13.4	13.4	13.3	13.2
2018 | Car
Claims Development [Line Items]
Total paid losses and ALAE, net	41.7	25.1	30.2	27.6	28.2	24.4	$ 16.8
2019 | Home and renters
Claims Development [Line Items]
Total paid losses and ALAE, net	46.2	46.2	46.3	46.3	46.1	36.4
2019 | Car
Claims Development [Line Items]
Total paid losses and ALAE, net	30.7	22.3	18.8	14.5	18.7	$ 13.5
2020 | Home and renters
Claims Development [Line Items]
Total paid losses and ALAE, net	52.1	52.0	51.3	50.2	43.1
2020 | Pet
Claims Development [Line Items]
Total paid losses and ALAE, net	0.7	0.7	0.7	0.6	0.4
2020 | Car
Claims Development [Line Items]
Total paid losses and ALAE, net	14.0	15.0	5.6	(0.9)	$ 5.2
2021 | Home and renters
Claims Development [Line Items]
Total paid losses and ALAE, net	57.8	56.7	53.4	37.8
2021 | Pet
Claims Development [Line Items]
Total paid losses and ALAE, net	9.5	9.5	9.4	7.6
2021 | Car
Claims Development [Line Items]
Total paid losses and ALAE, net	80.2	77.1	58.9	$ 38.4
2022 | Home and renters
Claims Development [Line Items]
Total paid losses and ALAE, net	90.7	85.5	52.7
2022 | Pet
Claims Development [Line Items]
Total paid losses and ALAE, net	25.1	25.1	21.8
2022 | Car
Claims Development [Line Items]
Total paid losses and ALAE, net	81.4	74.0	$ 45.4
2023 | Home and renters
Claims Development [Line Items]
Total paid losses and ALAE, net	122.3	88.9
2023 | Pet
Claims Development [Line Items]
Total paid losses and ALAE, net	48.9	45.8
2023 | Car
Claims Development [Line Items]
Total paid losses and ALAE, net	58.4	$ 43.2
2024 | Home and renters
Claims Development [Line Items]
Total paid losses and ALAE, net	89.1
2024 | Pet
Claims Development [Line Items]
Total paid losses and ALAE, net	67.6
2024 | Car
Claims Development [Line Items]
Total paid losses and ALAE, net	$ 31.8