Supplemental Information about Changes to Accumulated Other Comprehensive Income - Schedule of Change in Balance by Component (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	$ 5,227,754	$ 3,980,306	$ 4,486,803	$ 3,949,577
Other comprehensive income (loss) before reclassifications, net of tax	(293,313)	484,223	285,358	266,141
Reclassifications, net of tax	(1,810)	700	2,318	65,198
Other comprehensive income (loss)	(295,123)	484,923	287,676	331,339
Ending balance	4,638,625	4,623,131	4,638,625	4,623,131
Total
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	(2,189,620)	(2,943,897)	(2,772,419)	(2,790,313)
Ending balance	(2,484,743)	(2,458,974)	(2,484,743)	(2,458,974)
Available for Sale Assets
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	(1,271,213)	(1,249,399)	(827,596)	(1,420,672)
Other comprehensive income (loss) before reclassifications, net of tax	686,343	(842,527)	238,785	(736,046)
Reclassifications, net of tax	(1,903)	672	2,038	65,464
Other comprehensive income (loss)	684,440	(841,855)	240,823	(670,582)
Ending balance	(586,773)	(2,091,254)	(586,773)	(2,091,254)
Future Policy Benefits
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	(911,717)	(1,696,801)	(1,947,391)	(1,369,204)
Other comprehensive income (loss) before reclassifications, net of tax	(985,420)	1,332,976	50,254	1,005,379
Reclassifications, net of tax	0	0	0	0
Other comprehensive income (loss)	(985,420)	1,332,976	50,254	1,005,379
Ending balance	(1,897,137)	(363,825)	(1,897,137)	(363,825)
Foreign Exchange
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	(4,726)	1,353	4,719	(1,681)
Other comprehensive income (loss) before reclassifications, net of tax	5,764	(6,226)	(3,681)	(3,192)
Reclassifications, net of tax	0	0	0	0
Other comprehensive income (loss)	5,764	(6,226)	(3,681)	(3,192)
Ending balance	1,038	(4,873)	1,038	(4,873)
Pension Adjustments
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	(1,964)	950	(2,151)	1,244
Other comprehensive income (loss) before reclassifications, net of tax	0	0	0	0
Reclassifications, net of tax	93	28	280	(266)
Other comprehensive income (loss)	93	28	280	(266)
Ending balance	$ (1,871)	$ 978	$ (1,871)	$ 978