Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 742,934	$ 600,671	$ 393,626
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	(584,856)	(138,435)	178,761
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	(7,880)	4,472	26,440
Net decrease (increase) in expected credit losses	0	725	(991)
Net unrealized gains (losses) on investments	(576,976)	(143,632)	153,312
Other adjustments to comprehensive income (loss), net	84	0	(75)
Other comprehensive income (loss), net of tax	(576,892)	(143,632)	153,237
Comprehensive income	$ 166,042	$ 457,039	$ 546,863