Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Other comprehensive income (loss):
Other comprehensive (losses) gain, before tax	$ 120,238	$ (508,510)
Other comprehensive income (loss):
Other comprehensive (losses) gain, tax effect	(17,944)	75,013
Net of Tax
Balance, beginning of year	4,462,309	4,236,114
Other comprehensive income (loss):
Total other comprehensive income (loss)	102,294	(433,497)	$ (87,567)
Balance, end of year	5,102,550	4,462,309	4,236,114
Accumulated Other Comprehensive Income (Loss)
Before Tax
AOCI before tax, beginning of year	(443,230)	65,280
Other comprehensive income (loss):
AOCI before tax, end of year	(322,992)	(443,230)	65,280
Tax Effect
AOCI tax effect, beginning of year	60,440	(14,573)
Other comprehensive income (loss):
AOCI tax effect, end of year	42,496	60,440	(14,573)
Net of Tax
Balance, beginning of year	(382,790)	50,707	138,274
Other comprehensive income (loss):
Total other comprehensive income (loss)	102,294	(433,497)	(87,567)
Balance, end of year	(280,496)	(382,790)	$ 50,707
Accumulated Net Investment Gains (Losses) On Investments
Other comprehensive income (loss):
Unrealized holding (losses) gains arising during the year, before tax	113,034	(521,682)
Less: Reclassification adjustment for losses (gains) included in net income	7,204	13,172
Other comprehensive (losses) gain, before tax	120,238	(508,510)
Other comprehensive income (loss):
Unrealized holding (losses) gains arising during the year, tax effect	(16,633)	75,118
Less: Reclassification adjustment for losses (gains) included in net income	(1,311)	(105)
Other comprehensive (losses) gain, tax effect	(17,944)	75,013
Other comprehensive income (loss):
Unrealized holding (losses) gains arising during the year, net of tax	96,401	(446,564)
Less: Reclassification adjustment for losses (gains) included in net income	5,893	13,067
Total other comprehensive income (loss)	$ 102,294	$ (433,497)