Unpaid Loss and Loss Adjustment Expense - Claims Development Information, Paid Losses (Details) - USD ($) $ in Millions	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	$ 124.3
Ceded unpaid loss and LAE	124.6	$ 72.7	$ 36.3
Gross unpaid loss and LAE	256.2	97.9	46.3
Home and renters
Claims Development [Line Items]
Total paid losses and ALAE, net	218.8
Total unpaid loss and ALAE reserves, net	46.9
Ceded unpaid loss and LAE	101.0
Gross unpaid loss and LAE	147.9
Pet
Claims Development [Line Items]
Total paid losses and ALAE, net	31.9
Total unpaid loss and ALAE reserves, net	5.9
Ceded unpaid loss and LAE	11.3
Gross unpaid loss and LAE	17.2
Car
Claims Development [Line Items]
Total paid losses and ALAE, net	191.2
Total unpaid loss and ALAE reserves, net	71.5
Ceded unpaid loss and LAE	12.3
Gross unpaid loss and LAE	83.8
Fair value adjustment on insurance contract intangible liability	2.0
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
2016 | Car
Claims Development [Line Items]
Total paid losses and ALAE, net	1.9	1.9	1.7	1.7	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	1.6
2017 | Car
Claims Development [Line Items]
Total paid losses and ALAE, net	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	13.2	13.2
2018 | Car
Claims Development [Line Items]
Total paid losses and ALAE, net	30.2	27.6	28.2	24.4	$ 16.8
2019 | Home and renters
Claims Development [Line Items]
Total paid losses and ALAE, net	46.3	46.3	46.1	36.4
2019 | Car
Claims Development [Line Items]
Total paid losses and ALAE, net	18.8	14.5	18.7	$ 13.5
2020 | Home and renters
Claims Development [Line Items]
Total paid losses and ALAE, net	51.3	50.2	43.1
2020 | Pet
Claims Development [Line Items]
Total paid losses and ALAE, net	0.7	0.6	0.4
2020 | Car
Claims Development [Line Items]
Total paid losses and ALAE, net	5.6	(0.9)	$ 5.2
2021 | Home and renters
Claims Development [Line Items]
Total paid losses and ALAE, net	53.4	37.8
2021 | Pet
Claims Development [Line Items]
Total paid losses and ALAE, net	9.4	7.6
2021 | Car
Claims Development [Line Items]
Total paid losses and ALAE, net	58.9	$ 38.4
2022 | Home and renters
Claims Development [Line Items]
Total paid losses and ALAE, net	52.7
2022 | Pet
Claims Development [Line Items]
Total paid losses and ALAE, net	21.8
2022 | Car
Claims Development [Line Items]
Total paid losses and ALAE, net	$ 44.1