Unpaid Loss and Loss Adjustment Expense - Claims Development Information, Paid Losses (Details) - USD ($) $ in Millions	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	$ 141.4
Ceded unpaid loss and LAE	120.2	$ 124.6	$ 72.7
Gross unpaid loss and LAE	262.3	256.2	97.9
Home and renters
Claims Development [Line Items]
Total paid losses and ALAE, net	344.4
Total unpaid loss and ALAE reserves, net	63.4
Ceded unpaid loss and LAE	92.9
Gross unpaid loss and LAE	156.3
Pet
Claims Development [Line Items]
Total paid losses and ALAE, net	81.1
Total unpaid loss and ALAE reserves, net	6.2
Ceded unpaid loss and LAE	7.8
Gross unpaid loss and LAE	14.0
Car
Claims Development [Line Items]
Total paid losses and ALAE, net	283.5
Total unpaid loss and ALAE reserves, net	71.8
Ceded unpaid loss and LAE	19.5
Gross unpaid loss and LAE	91.3
Fair value adjustment on insurance contract intangible liability	1.2
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
2016 | Car
Claims Development [Line Items]
Total paid losses and ALAE, net	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	1.6
2017 | Car
Claims Development [Line Items]
Total paid losses and ALAE, net	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	13.3	13.2
2018 | Car
Claims Development [Line Items]
Total paid losses and ALAE, net	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	46.3	46.3	46.1	36.4
2019 | Car
Claims Development [Line Items]
Total paid losses and ALAE, net	22.3	18.8	14.5	18.7	$ 13.5
2020 | Home and renters
Claims Development [Line Items]
Total paid losses and ALAE, net	52.0	51.3	50.2	43.1
2020 | Pet
Claims Development [Line Items]
Total paid losses and ALAE, net	0.7	0.7	0.6	0.4
2020 | Car
Claims Development [Line Items]
Total paid losses and ALAE, net	15.0	5.6	(0.9)	$ 5.2
2021 | Home and renters
Claims Development [Line Items]
Total paid losses and ALAE, net	56.7	53.4	37.8
2021 | Pet
Claims Development [Line Items]
Total paid losses and ALAE, net	9.5	9.4	7.6
2021 | Car
Claims Development [Line Items]
Total paid losses and ALAE, net	77.1	58.9	$ 38.4
2022 | Home and renters
Claims Development [Line Items]
Total paid losses and ALAE, net	85.5	52.7
2022 | Pet
Claims Development [Line Items]
Total paid losses and ALAE, net	25.1	21.8
2022 | Car
Claims Development [Line Items]
Total paid losses and ALAE, net	74.0	$ 45.4
2023 | Home and renters
Claims Development [Line Items]
Total paid losses and ALAE, net	88.9
2023 | Pet
Claims Development [Line Items]
Total paid losses and ALAE, net	45.8
2023 | Car
Claims Development [Line Items]
Total paid losses and ALAE, net	$ 43.2