Investments - Security Holdings in an Unrealized Loss Position - Tabular Disclosure (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Fair Value
Fair Value - Less Than 12 Months	$ 415,794	$ 160,773
Fair Value - More Than 12 Months	60,008	9,346
Fair Value - Total	475,802	170,119
Unrealized Losses
Unrealized Losses - Less Than 12 Months	(42,947)	(2,188)
Unrealized Losses - More Than 12 Months	(11,260)	(517)
Unrealized Losses - Total	(54,207)	(2,705)
U.S. Governments
Fair Value
Fair Value - Less Than 12 Months	43,268	5,968
Fair Value - More Than 12 Months	6,330	1,457
Fair Value - Total	49,598	7,425
Unrealized Losses
Unrealized Losses - Less Than 12 Months	(1,673)	(147)
Unrealized Losses - More Than 12 Months	(750)	(43)
Unrealized Losses - Total	(2,423)	(190)
States, territories, and possessions
Fair Value
Fair Value - Less Than 12 Months	5,243	1,444
Fair Value - More Than 12 Months	1,470
Fair Value - Total	6,713	1,444
Unrealized Losses
Unrealized Losses - Less Than 12 Months	(618)	(63)
Unrealized Losses - More Than 12 Months	(340)
Unrealized Losses - Total	(958)	(63)
Political subdivisions
Fair Value
Fair Value - Less Than 12 Months	4,245	1,815
Fair Value - Total	4,245	1,815
Unrealized Losses
Unrealized Losses - Less Than 12 Months	(677)	(22)
Unrealized Losses - Total	(677)	(22)
Special revenue excluding mortgage/asset-backed securities
Fair Value
Fair Value - Less Than 12 Months	31,254	6,280
Fair Value - More Than 12 Months	4,821
Fair Value - Total	36,075	6,280
Unrealized Losses
Unrealized Losses - Less Than 12 Months	(4,841)	(76)
Unrealized Losses - More Than 12 Months	(1,493)
Unrealized Losses - Total	(6,334)	(76)
Corporate and other
Fair Value
Fair Value - Less Than 12 Months	200,092	94,020
Fair Value - More Than 12 Months	39,574	5,570
Fair Value - Total	239,666	99,590
Unrealized Losses
Unrealized Losses - Less Than 12 Months	(21,298)	(1,468)
Unrealized Losses - More Than 12 Months	(7,595)	(423)
Unrealized Losses - Total	(28,893)	(1,891)
Mortgage/asset-backed securities
Fair Value
Fair Value - Less Than 12 Months	131,692	51,246
Fair Value - More Than 12 Months	7,813	2,319
Fair Value - Total	139,505	53,565
Unrealized Losses
Unrealized Losses - Less Than 12 Months	(13,840)	(412)
Unrealized Losses - More Than 12 Months	(1,082)	(51)
Unrealized Losses - Total	$ (14,922)	$ (463)

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