Investments - Security Holdings in an Unrealized Loss Position - Tabular Disclosure (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Fair Value
Fair Value - Less Than 12 Months	$ 251,239	$ 384,693
Fair Value - More Than 12 Months	246,689	99,986
Fair Value - Total	497,928	484,679
Unrealized Losses
Unrealized Losses - Less Than 12 Months	(11,517)	(31,558)
Unrealized Losses - More Than 12 Months	(28,898)	(15,365)
Unrealized Losses - Total	(40,415)	(46,923)
U.S. Governments
Fair Value
Fair Value - Less Than 12 Months	25,586	41,077
Fair Value - More Than 12 Months	23,438	6,853
Fair Value - Total	49,024	47,930
Unrealized Losses
Unrealized Losses - Less Than 12 Months	(391)	(1,523)
Unrealized Losses - More Than 12 Months	(1,372)	(730)
Unrealized Losses - Total	(1,763)	(2,253)
States, territories, and possessions
Fair Value
Fair Value - Less Than 12 Months	3,310	3,227
Fair Value - Total	3,310	3,227
Unrealized Losses
Unrealized Losses - Less Than 12 Months	(466)	(552)
Unrealized Losses - Total	(466)	(552)
Political subdivisions
Fair Value
Fair Value - Less Than 12 Months	454	4,298
Fair Value - More Than 12 Months	3,980
Fair Value - Total	4,434	4,298
Unrealized Losses
Unrealized Losses - Less Than 12 Months	(21)	(621)
Unrealized Losses - More Than 12 Months	(460)
Unrealized Losses - Total	(481)	(621)
Special revenue excluding mortgage/asset-backed securities
Fair Value
Fair Value - Less Than 12 Months	8,050	25,091
Fair Value - More Than 12 Months	22,928	5,080
Fair Value - Total	30,978	30,171
Unrealized Losses
Unrealized Losses - Less Than 12 Months	(595)	(3,287)
Unrealized Losses - More Than 12 Months	(2,974)	(1,200)
Unrealized Losses - Total	(3,569)	(4,487)
Corporate and other
Fair Value
Fair Value - Less Than 12 Months	136,179	192,185
Fair Value - More Than 12 Months	120,285	55,605
Fair Value - Total	256,464	247,790
Unrealized Losses
Unrealized Losses - Less Than 12 Months	(6,630)	(15,667)
Unrealized Losses - More Than 12 Months	(14,603)	(8,481)
Unrealized Losses - Total	(21,233)	(24,148)
Mortgage/asset-backed securities
Fair Value
Fair Value - Less Than 12 Months	77,660	118,815
Fair Value - More Than 12 Months	76,058	32,448
Fair Value - Total	153,718	151,263
Unrealized Losses
Unrealized Losses - Less Than 12 Months	(3,414)	(9,908)
Unrealized Losses - More Than 12 Months	(9,489)	(4,954)
Unrealized Losses - Total	$ (12,903)	$ (14,862)

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