Shareholders' equity AOCI (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Jun. 30, 2025	Dec. 31, 2024	Jun. 30, 2024	Dec. 31, 2023
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income, before income tax	$ 1,286	$ 3,205	$ 3,960	$ 1,601
Other Comprehensive Income (Loss), Tax	40	150	116	112
Other Comprehensive Income (Loss), Net of Tax	1,246	3,055	3,844	1,489
Total shareholders' equity	77,811	70,120	77,811	70,120		$ 68,394
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total shareholders' equity	(1,940)	(2,042)	(1,940)	(2,042)	$ (2,772)	(4,552)	$ (5,301)	$ (4,177)
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-Sale, Including Noncontrolling Interest
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other Comprehensive Income (Loss), before Reclassifications, before Tax	837	3,419	2,598	2,139
Net Realized Gains (Losses) Reclassified from AOCI	(31)	(40)	(157)	(154)
Other comprehensive income, before income tax	868	3,459	2,755	2,293
Other Comprehensive Income (Loss), Tax	52	198	163	149
Other Comprehensive Income (Loss), Net of Tax	816	3,261	2,592	2,144
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-Sale, Noncontrolling Interest
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other Comprehensive Income (Loss), Net of Tax	(16)	2	(20)	9
AOCI, Liability for Future Policy Benefit, Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total shareholders' equity	(462)	(527)	(462)	(527)	(746)	(539)	66	51
AOCI, Liability for Future Policy Benefit, Including Noncontrolling Interest
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income, before income tax	305	(672)	53	(672)
Other Comprehensive Income (Loss), Tax	(26)	(36)	(47)	(14)
Other Comprehensive Income (Loss), Net of Tax	331	(636)	100	(658)
AOCI, Liability for Future Policy Benefit, Noncontrolling Interest
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other Comprehensive Income (Loss), Net of Tax	47	(43)	23	(80)
AOCI, Market Risk Benefit, Instrument-Specific Credit Risk, Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total shareholders' equity	(19)	(20)	(19)	(20)	(12)	(16)	(13)	(22)
AOCI, Market Risk Benefit, Instrument-Specific Credit Risk, Including Noncontrolling Interest
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income, before income tax	(9)	(8)	(4)	2
Other Comprehensive Income (Loss), Tax	(2)	(1)	(1)	0
Other Comprehensive Income (Loss), Net of Tax	(7)	(7)	(3)	2
AOCI, Market Risk Benefit, Instrument-Specific Credit Risk, Noncontrolling Interest
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other Comprehensive Income (Loss), Net of Tax	0	0	0	0
Cumulative Foreign Currency Translation Adjustment [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total shareholders' equity	(2,857)	(2,952)	(2,857)	(2,952)	(2,919)	(4,025)	(3,342)	(2,945)
Accumulated Foreign Currency Adjustment Including Portion Attributable to Noncontrolling Interest
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other Comprehensive Income (Loss), before Reclassifications, before Tax	136	450	1,306	6
Net Realized Gains (Losses) Reclassified from AOCI	8	5	23	11
Other comprehensive income, before income tax	128	445	1,283	(5)
Other Comprehensive Income (Loss), Tax	17	(7)	26	(19)
Other Comprehensive Income (Loss), Net of Tax	111	452	1,257	14
Accumulated Foreign Currency Adjustment Attributable to Noncontrolling Interest
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other Comprehensive Income (Loss), Net of Tax	49	62	89	21
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total shareholders' equity	(43)	(25)	(43)	(25)	(40)	50	(11)	(13)
Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other Comprehensive Income (Loss), before Reclassifications, before Tax	(17)	42	98	(12)
Net Realized Gains (Losses) Reclassified from AOCI	(14)	60	215	3
Other comprehensive income, before income tax	(3)	(18)	(117)	(15)
Other Comprehensive Income (Loss), Tax	0	(4)	(24)	(3)
Other Comprehensive Income (Loss), Net of Tax	(3)	(14)	(93)	(12)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Noncontrolling Interest
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other Comprehensive Income (Loss), Net of Tax	0	0	0	0
Postretirement Benefit Liability Adjustment [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total shareholders' equity	429	296	429	296	431	438	297	297
Accumulated Defined Benefit Plans Adjustment Including Portion Attributable to Noncontrolling Interest
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income, before income tax	(3)	(1)	(10)	(2)
Other Comprehensive Income (Loss), Tax	(1)	0	(1)	(1)
Other Comprehensive Income (Loss), Net of Tax	(2)	(1)	(9)	(1)
Accumulated Defined Benefit Plans Adjustment Attributable to Noncontrolling Interest
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other Comprehensive Income (Loss), Net of Tax	0	0	0	0
Accumulated Other Comprehensive Income (Loss) [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other Comprehensive Income (Loss), Net of Tax	1,166	3,034	3,752	1,539
Total shareholders' equity	$ (4,892)	$ (5,270)	$ (4,892)	$ (5,270)	$ (6,058)	$ (8,644)	$ (8,304)	$ (6,809)