Reserves for Unpaid Losses and Loss Adjustment Expenses (Causes for Prior Accident Year Reserve Development by Segment) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Total (favorable) unfavorable net prior year development	$ 7,691	$ (2,086)
Specialty Commercial Segment [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Total (favorable) unfavorable net prior year development	6,380	(1,899)
Standard Commercial Segment [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Total (favorable) unfavorable net prior year development	(262)	(1,361)
Personal Segment [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Total (favorable) unfavorable net prior year development	$ 1,573	$ 1,174