Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 151,892,000	$ 156,582,000	$ 456,149,000	$ 460,426,000
Other comprehensive income (loss), net of tax (Note 15)
Unrealized holding gains (losses) on investments arising during the period for which an allowance for expected losses has not been recognized	144,659,000	(99,603,000)	92,930,000	(74,874,000)
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	448,000	(2,207,000)	(4,889,000)	(10,412,000)
Net unrealized gains (losses) on investments	144,211,000	(97,396,000)	97,819,000	(64,462,000)
Other adjustments to comprehensive income (loss), net	0	0	(68,000)	179,000
Other comprehensive income (loss), net of tax	144,211,000	(97,396,000)	97,751,000	(64,283,000)
Comprehensive income (loss)	$ 296,103,000	$ 59,186,000	$ 553,900,000	$ 396,143,000