Unpaid Losses and Loss Adjustment Expenses - Narrative (Details) - USD ($)	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Liability For Claims And Claims Adjustment Expense [Line Items]
Increase in net losses and loss adjustment expenses	$ 6,000,000.0			$ 11,100,000
Percentage of loss adjustment expenses increased	50.10%			42.20%
Losses and loss adjustment expenses, net	$ 17,926,000		$ 11,945,000	$ 37,288,000	$ 26,214,000
Prior year adjustments	$ 6,210,000		3,037,000	11,988,000	6,786,000	$ 1,900,000	$ 1,900,000	$ 2,400,000	$ 1,900,000
Winter Storm Uri
Liability For Claims And Claims Adjustment Expense [Line Items]
Losses and loss adjustment expenses, net		$ 2,000,000.0
Commercial Lines1
Liability For Claims And Claims Adjustment Expense [Line Items]
Prior year adjustments			$ 3,000,000.0	11,400,000	$ 6,700,000
Personal Lines
Liability For Claims And Claims Adjustment Expense [Line Items]
Prior year adjustments				$ 636,000