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, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	$ 5,419,030	$ 5,227,754	$ 5,305,520	$ 4,486,803
Other comprehensive income (loss) before reclassifications, net of tax	3,080	(293,313)	43,095	285,358
Reclassifications, net of tax	7,897	(1,810)	13,734	2,318
Other comprehensive income (loss)	10,977	(295,123)	56,829	287,676
Ending balance	5,689,088	4,638,625	5,689,088	4,638,625
Total
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	(1,983,868)	(2,189,620)	(2,029,720)	(2,772,419)
Ending balance	(1,972,891)	(2,484,743)	(1,972,891)	(2,484,743)
Available for Sale Assets
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	(1,251,427)	(1,271,213)	(1,319,618)	(827,596)
Other comprehensive income (loss) before reclassifications, net of tax	342,044	686,343	404,498	238,785
Reclassifications, net of tax	7,847	(1,903)	13,584	2,038
Other comprehensive income (loss)	349,891	684,440	418,082	240,823
Ending balance	(901,536)	(586,773)	(901,536)	(586,773)
Future Policy Benefits
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	(746,269)	(911,717)	(709,042)	(1,947,391)
Other comprehensive income (loss) before reclassifications, net of tax	(334,519)	(985,420)	(371,746)	50,254
Reclassifications, net of tax	0	0	0	0
Other comprehensive income (loss)	(334,519)	(985,420)	(371,746)	50,254
Ending balance	(1,080,788)	(1,897,137)	(1,080,788)	(1,897,137)
Foreign Exchange
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	(6,969)	(4,726)	(21,757)	4,719
Other comprehensive income (loss) before reclassifications, net of tax	(4,445)	5,764	10,343	(3,681)
Reclassifications, net of tax	0	0	0	0
Other comprehensive income (loss)	(4,445)	5,764	10,343	(3,681)
Ending balance	(11,414)	1,038	(11,414)	1,038
Pension Adjustments
Increase (Decrease) in AOCI, Net of Tax
Beginning balance	20,797	(1,964)	20,697	(2,151)
Other comprehensive income (loss) before reclassifications, net of tax	0	0	0	0
Reclassifications, net of tax	50	93	150	280
Other comprehensive income (loss)	50	93	150	280
Ending balance	$ 20,847	$ (1,871)	$ 20,847	$ (1,871)