Investments - Securities with Gross Unrealized Loss Position (Details) $ in Thousands	Sep. 30, 2021 USD ($) security item
Net Investment Income [Line Items]
Number of securities in an unrealized loss position | security	260
Unrealized loss position for 12 months or longer | item	0
Debt Securities
Net Investment Income [Line Items]
Less Than Twelve Months, Gross Unrealized Loss	$ (155)
Less Than Twelve Months, Fair Value	31,883
Total, Gross Unrealized Loss	(155)
Total, Fair Value	31,883
U.S. government obligations
Net Investment Income [Line Items]
Less Than Twelve Months, Gross Unrealized Loss	(27)
Less Than Twelve Months, Fair Value	6,073
Total, Gross Unrealized Loss	(27)
Total, Fair Value	6,073
Obligations of states, municipalities and political subdivisions
Net Investment Income [Line Items]
Less Than Twelve Months, Gross Unrealized Loss	(12)
Less Than Twelve Months, Fair Value	1,274
Total, Gross Unrealized Loss	(12)
Total, Fair Value	1,274
Industrial and miscellaneous
Net Investment Income [Line Items]
Less Than Twelve Months, Gross Unrealized Loss	(48)
Less Than Twelve Months, Fair Value	11,978
Total, Gross Unrealized Loss	(48)
Total, Fair Value	11,978
Residential and commercial mortgage-backed securities
Net Investment Income [Line Items]
Less Than Twelve Months, Gross Unrealized Loss	(55)
Less Than Twelve Months, Fair Value	9,108
Total, Gross Unrealized Loss	(55)
Total, Fair Value	9,108
Other loan-backed and structured securities
Net Investment Income [Line Items]
Less Than Twelve Months, Gross Unrealized Loss	(13)
Less Than Twelve Months, Fair Value	3,450
Total, Gross Unrealized Loss	(13)
Total, Fair Value	$ 3,450