Accumulated Other Comprehensive Income (Loss) - Schedule Of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Net of Tax
Balance at beginning of period				$ (350,238)
Other comprehensive income (loss)
Unrealized holding gains (losses) on investments arising during the period for which an allowance for expected credit losses has not been recognized		$ 20,151	$ (17,242)	73,772	$ (51,729)
Less: Reclassification adjustment for net gains (losses) on investments included in net income:
Net realized gains (losses) on disposals and non-credit related impairment losses		(1,624)	(2,427)	(3,480)	(5,337)
Net unrealized gains (losses) on investments		21,775	(14,815)	77,252	(46,392)
Other adjustments to other comprehensive income (loss)		0	0	45	(68)
Other comprehensive income (loss), net of tax		21,775	(14,815)	77,297	(46,460)
Balance at end of period		(272,941)		(272,941)
Other Comprehensive Income (Loss)
Before Tax
Balance at beginning of period		(373,058)	(458,856)	(443,340)	(418,799)
Other comprehensive income (loss)
Unrealized holding gains (losses) on investments arising during the period for which an allowance for expected credit losses has not been recognized		25,507	(21,825)	93,382	(65,480)
Less: Reclassification adjustment for net gains (losses) on investments included in net income
Net realized gains (losses) on disposals and non-credit related impairment losses	[1]	(2,056)	(3,071)	(4,405)	(6,755)
Net unrealized gains (losses) on investments	[1]	27,563	(18,754)	97,787	(58,725)
Other adjustments to comprehensive income (loss), net	[1]	0	(0)	58	(86)
Other comprehensive income (loss)	[1]	27,563	(18,754)	97,845	(58,811)
Balance at end of period	[1]	(345,495)	(477,610)	(345,495)	(477,610)
Tax Effect
Balance at beginning of period		(78,342)	(96,360)	(93,102)	(87,948)
Other comprehensive income (loss)
Unrealized holding gains (losses) on investments arising during the period for which an allowance for expected credit losses has not been recognized		5,356	(4,583)	19,610	(13,751)
Less: Reclassification adjustment for net gains (losses) on investments included in net income:
Net realized gains (losses) on disposals and non-credit related impairment losses	[1]	(432)	(644)	(925)	(1,418)
Net unrealized gains (losses) on investments	[1]	5,788	(3,939)	20,535	(12,333)
Other adjustments to comprehensive income (loss), net	[1]	0	0	13	(18)
Other comprehensive income (loss)	[1]	5,788	(3,939)	20,548	(12,351)
Balance at end of period	[1]	(72,554)	(100,299)	(72,554)	(100,299)
Net of Tax
Balance at beginning of period		(294,716)	(362,496)	(350,238)	(330,851)
Other comprehensive income (loss)
Unrealized holding gains (losses) on investments arising during the period for which an allowance for expected credit losses has not been recognized		20,151	(17,242)	73,772	(51,729)
Less: Reclassification adjustment for net gains (losses) on investments included in net income:
Net realized gains (losses) on disposals and non-credit related impairment losses	[1]	(1,624)	(2,427)	(3,480)	(5,337)
Net unrealized gains (losses) on investments	[1]	21,775	(14,815)	77,252	(46,392)
Other adjustments to other comprehensive income (loss)	[1]	0	0	45	(68)
Other comprehensive income (loss), net of tax	[1]	21,775	(14,815)	77,297	(46,460)
Balance at end of period	[1]	$ (272,941)	$ (377,311)	$ (272,941)	$ (377,311)

[1] Included in net gains (losses) on investments and other financial instruments in our condensed consolidated statements of operations.