Stockholders' Equity (Schedule of Accumulated Other Comprehensive Income (Loss) by Component) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period			$ 11,621
Other comprehensive income (loss) before reclassifications	$ 125	$ 162	(138)	$ 358
Amounts reclassified from accumulated other comprehensive income (loss) net of tax	(8)	(37)	(20)	(47)
Other comprehensive income (loss) after tax (expense) benefit	133	199	(118)	405
Total stockholder's equity at end of period	11,186	10,661	11,186	10,661
Reclassification from AOCI, tax	3	13	6	14
Tax (expense) benefit on other comprehensive income (loss)	(42)	(23)	18	(65)
Accumulated other comprehensive income (loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period	(1,349)	(1,785)	(1,098)	(1,991)
Total stockholder's equity at end of period	(1,216)	(1,586)	(1,216)	(1,586)
Net unrealized gains (losses) on investments | Investments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period	(22)	(16)	(15)	(13)
Other comprehensive income (loss) before reclassifications	(3)	(5)	(15)	(10)
Amounts reclassified from accumulated other comprehensive income (loss) net of tax	(2)	(6)	(7)	(8)
Other comprehensive income (loss) after tax (expense) benefit	(1)	1	(8)	(2)
Total stockholder's equity at end of period	(23)	(15)	(23)	(15)
Reclassification from AOCI, tax	1	2	2	2
Tax (expense) benefit on other comprehensive income (loss)	0	0	2	1
Net unrealized gains (losses) on investments | Other investments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period	(1,413)	(1,593)	(988)	(1,876)
Other comprehensive income (loss) before reclassifications	186	42	(245)	319
Amounts reclassified from accumulated other comprehensive income (loss) net of tax	(4)	(30)	(10)	(36)
Other comprehensive income (loss) after tax (expense) benefit	190	72	(235)	355
Total stockholder's equity at end of period	(1,223)	(1,521)	(1,223)	(1,521)
Reclassification from AOCI, tax	1	10	3	11
Tax (expense) benefit on other comprehensive income (loss)	(51)	(22)	64	(96)
Pension and postretirement benefits
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period	(165)	(189)	(166)	(191)
Other comprehensive income (loss) before reclassifications	(2)	0	(2)	0
Amounts reclassified from accumulated other comprehensive income (loss) net of tax	(2)	(1)	(3)	(3)
Other comprehensive income (loss) after tax (expense) benefit	0	1	1	3
Total stockholder's equity at end of period	(165)	(188)	(165)	(188)
Reclassification from AOCI, tax	1	1	1	1
Tax (expense) benefit on other comprehensive income (loss)	0	(1)	0	(1)
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	406	239	192	353
Other comprehensive income (loss) before reclassifications	(34)	(3)	180	(117)
Amounts reclassified from accumulated other comprehensive income (loss) net of tax	0	0	0	0
Other comprehensive income (loss) after tax (expense) benefit	(34)	(3)	180	(117)
Total stockholder's equity at end of period	372	236	372	236
Reclassification from AOCI, tax	0	0	0	0
Tax (expense) benefit on other comprehensive income (loss)	9	0	(48)	31
Cumulative foreign currency translation adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period	(155)	(226)	(121)	(264)
Other comprehensive income (loss) before reclassifications	(22)	128	(56)	166
Amounts reclassified from accumulated other comprehensive income (loss) net of tax	0	0	0	0
Other comprehensive income (loss) after tax (expense) benefit	(22)	128	(56)	166
Total stockholder's equity at end of period	(177)	(98)	(177)	(98)
Reclassification from AOCI, tax	0	0	0	0
Tax (expense) benefit on other comprehensive income (loss)	$ 0	$ 0	$ 0	$ 0