Reserve for Loss and Loss Expense - Narrative (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Incurred loss and loss expense for claims occurring in the prior year	$ (27,219)	$ 34,648
Property lines
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Incurred loss and loss expense for claims occurring in the prior year		(15,400)
Casualty lines
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Incurred loss and loss expense for claims occurring in the prior year		50,000
Casualty lines \| Standard Commercial Lines \| Commercial automobile
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Incurred loss and loss expense for claims occurring in the prior year		25,000
Casualty lines \| Standard Commercial Lines \| General liability
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Incurred loss and loss expense for claims occurring in the prior year		20,000
Casualty lines \| Standard Personal Lines \| Personal automobile
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Incurred loss and loss expense for claims occurring in the prior year		$ 5,000