Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Before Tax
Unrealized holding gains (losses) on investments arising during the period for which an allowance for expected credit losses has not been recognized	$ (43,655)	$ 83,359
Net realized gains (losses) on disposals and non-credit related impairment losses	(3,684)	(5,232)
Net unrealized gains (losses) on investments	(39,971)	88,591
Other adjustments to comprehensive income (loss), net	(86)	227
Other comprehensive income (loss)	(40,057)	88,818
Tax Effect
Unrealized holding gains (losses) on investments arising during the period for which an allowance for expected credit losses has not been recognized	(9,168)	17,505
Net realized gains (losses) on disposals and non-credit related impairment losses	(774)	(1,099)
Net unrealized gains (losses) on investments	(8,394)	18,604
Other adjustments to comprehensive income (loss), net	(18)	48
Other comprehensive income (loss)	(8,412)	18,652
Net of Tax
Balance at beginning and end of the period	(362,496)		$ (330,851)
Unrealized holding gains (losses) on investments arising during the period for which an allowance for expected credit losses has not been recognized	(34,487)	65,854
Net realized gains (losses) on disposals and non-credit related impairment losses	(2,910)	(4,133)
Net unrealized gains (losses) on investments	(31,577)	69,987
Other adjustments to other comprehensive income (loss)	(68)	179
Other comprehensive income (loss), net of tax	(31,645)	70,166
AOCI Attributable to Parent
Before Tax
Balance at beginning of period	(418,799)	(578,228)
Balance at end of period	(458,856)	(489,410)
Tax Effect
Balance at beginning of period	(87,948)	(121,429)
Balance at end of period	(96,360)	(102,777)
Net of Tax
Balance at beginning and end of the period	(362,496)	(386,633)	$ (330,851)	$ (456,799)
Net unrealized gains (losses) on investments	$ (31,577)	$ 69,987