Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Other comprehensive income (loss):
Other comprehensive loss, before tax	$ (158,503)	$ 44,216	$ (397,406)	$ (25,188)
Other comprehensive income (loss):
Other comprehensive income, tax effect	24,235	(7,856)	60,132	2,345
Net of Tax
Balance, beginning of period			4,236,114
Other comprehensive income (loss):
Total other comprehensive income (loss)	(134,268)	36,360	(337,274)	(22,843)
Balance, end of period	4,271,995	4,084,828	4,271,995	4,084,828
Accumulated Other Comprehensive Income (Loss)
Before Tax
AOCI before tax, beginning of period	(173,623)	98,920	65,280	168,324
Other comprehensive income (loss):
AOCI before tax, end of period	(332,126)	143,136	(332,126)	143,136
Tax Effect
AOCI tax effect, beginning of period	21,324	(19,849)	(14,573)	(30,050)
Other comprehensive income (loss):
AOCI tax effect, end of period	45,559	(27,705)	45,559	(27,705)
Net of Tax
Balance, beginning of period	(152,299)	79,071	50,707	138,274
Other comprehensive income (loss):
Total other comprehensive income (loss)	(134,268)	36,360	(337,274)	(22,843)
Balance, end of period	(286,567)	115,431	(286,567)	115,431
Accumulated Net Investment Gains (Losses) On Investments
Other comprehensive income (loss):
Unrealized holding gains (losses) arising during the period	(158,974)	43,963	(405,229)	(24,800)
Less: Reclassification adjustment for losses (gains) included in net income, before tax	471	253	7,823	(388)
Other comprehensive loss, before tax	(158,503)	44,216	(397,406)	(25,188)
Other comprehensive income (loss):
Unrealized holding gains (losses) arising during the period	24,322	(7,826)	59,152	2,375
Less: Reclassification adjustment for losses (gains) included in net income, tax effect	(87)	(30)	980	(30)
Other comprehensive income, tax effect	24,235	(7,856)	60,132	2,345
Other comprehensive income (loss):
Unrealized holding gains (losses) arising during the period	(134,652)	36,137	(346,077)	(22,425)
Less: Reclassification adjustment for losses (gains) included in net income, net of tax	384	223	8,803	(418)
Total other comprehensive income (loss)	$ (134,268)	$ 36,360	$ (337,274)	$ (22,843)

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