Accumulated Other Comprehensive Income (Loss) by Component (Schedule of Accumulated Other Comprehensive Income (Loss) by Component) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period			$ 10,513
Other comprehensive income (loss) before reclassifications	$ 365	$ 685	723	$ 763
Amounts reclassified from accumulated other comprehensive income (loss) net of tax	(10)	(25)	(57)	(72)
Other comprehensive income (loss) after tax (expense) benefit	375	710	780	835
Total stockholder's equity at end of period	11,322	10,758	11,322	10,758
Reclassification from AOCI, tax	2	8	16	19
Tax (expense) benefit on other comprehensive income (loss)	(109)	(177)	(174)	(219)
Accumulated other comprehensive income (loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period	(1,586)	(2,547)	(1,991)	(2,672)
Total stockholder's equity at end of period	(1,211)	(1,837)	(1,211)	(1,837)
Net unrealized gains (losses) on investments | Net unrealized gains (losses) on investments with an allowance for credit losses
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period	(15)	(10)	(13)	(12)
Other comprehensive income (loss) before reclassifications	(1)	(9)	(11)	(14)
Amounts reclassified from accumulated other comprehensive income (loss) net of tax	(4)	(6)	(12)	(13)
Other comprehensive income (loss) after tax (expense) benefit	3	(3)	1	(1)
Total stockholder's equity at end of period	(12)	(13)	(12)	(13)
Reclassification from AOCI, tax	2	2	4	4
Tax (expense) benefit on other comprehensive income (loss)	(1)	1	0	0
Net unrealized gains (losses) on investments | Net unrealized gains and losses on other investments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period	(1,521)	(2,074)	(1,876)	(1,613)
Other comprehensive income (loss) before reclassifications	554	1,254	873	765
Amounts reclassified from accumulated other comprehensive income (loss) net of tax	(4)	(11)	(40)	(39)
Other comprehensive income (loss) after tax (expense) benefit	558	1,265	913	804
Total stockholder's equity at end of period	(963)	(809)	(963)	(809)
Reclassification from AOCI, tax	0	3	11	10
Tax (expense) benefit on other comprehensive income (loss)	(148)	(340)	(244)	(216)
Pension and postretirement benefits
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period	(188)	(513)	(191)	(525)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassified from accumulated other comprehensive income (loss) net of tax	(2)	(8)	(5)	(20)
Other comprehensive income (loss) after tax (expense) benefit	2	8	5	20
Total stockholder's equity at end of period	(186)	(505)	(186)	(505)
Reclassification from AOCI, tax	0	3	1	5
Tax (expense) benefit on other comprehensive income (loss)	0	(3)	(1)	(5)
Cumulative impact of changes in discount rates used to measure long duration contracts
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period	236	255	353	(359)
Other comprehensive income (loss) before reclassifications	(150)	(623)	(267)	(9)
Amounts reclassified from accumulated other comprehensive income (loss) net of tax	0	0	0	0
Other comprehensive income (loss) after tax (expense) benefit	(150)	(623)	(267)	(9)
Total stockholder's equity at end of period	86	(368)	86	(368)
Reclassification from AOCI, tax	0	0	0	0
Tax (expense) benefit on other comprehensive income (loss)	40	165	71	2
Cumulative foreign currency translation adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period	(98)	(205)	(264)	(163)
Other comprehensive income (loss) before reclassifications	(38)	63	128	21
Amounts reclassified from accumulated other comprehensive income (loss) net of tax	0	0	0	0
Other comprehensive income (loss) after tax (expense) benefit	(38)	63	128	21
Total stockholder's equity at end of period	(136)	(142)	(136)	(142)
Reclassification from AOCI, tax	0	0	0	0
Tax (expense) benefit on other comprehensive income (loss)	$ 0	$ 0	$ 0	$ 0