Unpaid Loss and Loss Adjustment Expense - Claims Development Information, Paid Losses (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Claims Development [Line Items]
Ceded unpaid loss and LAE	$ 72.7	$ 36.3	$ 18.5
Unpaid losses and loss adjustment expenses	97.9	46.3	28.2
Home
Claims Development [Line Items]
Total paid losses and ALAE, net	149.2
Total unpaid loss and ALAE reserves, net	22.9
Ceded unpaid loss and LAE	66.7
Unpaid losses and loss adjustment expenses	89.6
Pet
Claims Development [Line Items]
Total paid losses and ALAE, net	8.2
Total unpaid loss and ALAE reserves, net	2.3
Ceded unpaid loss and LAE	6.0
Unpaid losses and loss adjustment expenses	8.3
2016 | Home
Claims Development [Line Items]
Total paid losses and ALAE, net	0.0	0.0	0.0	$ 0.0	$ 0.0	$ 0.0
2017 | Home
Claims Development [Line Items]
Total paid losses and ALAE, net	1.7	1.7	1.7	1.7	$ 1.6
2018 | Home
Claims Development [Line Items]
Total paid losses and ALAE, net	13.4	13.4	13.4	$ 13.2
2019 | Home
Claims Development [Line Items]
Total paid losses and ALAE, net	46.2	46.1	$ 36.4
2020 | Home
Claims Development [Line Items]
Total paid losses and ALAE, net	50.0	42.9
2020 | Pet
Claims Development [Line Items]
Total paid losses and ALAE, net	0.7	$ 0.4
2021
Claims Development [Line Items]
Total paid losses and ALAE, net	45.4
2021 | Home
Claims Development [Line Items]
Total paid losses and ALAE, net	37.9
2021 | Pet
Claims Development [Line Items]
Total paid losses and ALAE, net	$ 7.5