Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Net of Tax
Balance at beginning and end of period	$ (456,799)	$ 120,093
Other comprehensive income (loss)
Unrealized holding gains (losses) arising during the period, net of tax	(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
Other Comprehensive Income (Loss)
Before Tax
Balance at beginning of period	152,016	333,829	139,858
Other comprehensive income (loss)
Unrealized holding gains (losses) arising during the period, before tax	(740,324)	(175,234)	226,280
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	(9,974)	5,661	33,468
Net decrease (increase) in expected credit losses		918	(1,254)
Net unrealized gains on investments	(730,350)	(181,813)	194,066
Other adjustments to comprehensive income, net	106		(95)
Other comprehensive income (loss)	(730,244)	(181,813)	193,971
Balance at end of period	(578,228)	152,016	333,829
Tax Effect
Balance at beginning of period	31,923	70,104	29,370
Other comprehensive income (loss)
Unrealized holding gains (losses) arising during the period, tax	(155,468)	(36,799)	47,519
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	(2,094)	1,189	7,028
Net decrease (increase) in expected credit losses		193	(263)
Net unrealized gains on investments	(153,374)	(38,181)	40,754
Other adjustments to comprehensive income, net	22		(20)
Other comprehensive income (loss)	(153,352)	(38,181)	40,734
Balance at end of period	(121,429)	31,923	70,104
Net of Tax
Balance at beginning and end of period	(456,799)	120,093	263,725	$ 110,488
Other comprehensive income (loss)
Unrealized holding gains (losses) arising during the period, net of tax	(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		725	(991)
Net unrealized gains (losses) on investments	(576,976)	(143,632)	153,312
Other adjustments to comprehensive income (loss), net	84		(75)
Other comprehensive income (loss), net of tax	$ (576,892)	$ (143,632)	$ 153,237