Shareholders' equity AOCI (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance – beginning of period, net of tax	$ 59,507
Other comprehensive income (loss), before income tax	(614)	$ 1,422
Other Comprehensive Income (Loss), Tax	(9)	132
Other Comprehensive Income (Loss), Net of Tax	(605)	1,290
Balance – end of period, net of tax	60,535	52,987
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance – beginning of period, net of tax	(4,177)	(7,279)
Balance – end of period, net of tax	(4,825)	(5,659)
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	(796)	1,606
Net Realized Gains (Losses) Reclassified from AOCI	(119)	(180)
Other comprehensive income (loss), before income tax	(677)	1,786
Other Comprehensive Income (Loss), Tax	(42)	166
Other Comprehensive Income (Loss), Net of Tax	(635)	1,620
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	13	0
AOCI, Liability for Future Policy Benefit, Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance – beginning of period, net of tax	51	(75)
Balance – end of period, net of tax	11	(205)
AOCI, Liability for Future Policy Benefit, Including Noncontrolling Interest
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss), before income tax	(53)	(151)
Other Comprehensive Income (Loss), Tax	20	(21)
Other Comprehensive Income (Loss), Net of Tax	(73)	(130)
AOCI, Liability for Future Policy Benefit, Noncontrolling Interest
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other Comprehensive Income (Loss), Net of Tax	(33)	0
AOCI, Market Risk Benefit, Instrument-Specific Credit Risk, Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance – beginning of period, net of tax	(22)	(24)
Balance – end of period, net of tax	(17)	(27)
AOCI, Market Risk Benefit, Instrument-Specific Credit Risk, Including Noncontrolling Interest
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other Comprehensive Income (Loss), Net of Tax	5	(3)
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
Cumulative Foreign Currency Translation Adjustment [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance – beginning of period, net of tax	(2,945)	(2,966)
Balance – end of period, net of tax	(2,864)	(3,136)
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	83	(174)
Net Realized Gains (Losses) Reclassified from AOCI	3	3
Other comprehensive income (loss), before income tax	80	(177)
Other Comprehensive Income (Loss), Tax	7	(7)
Other Comprehensive Income (Loss), Net of Tax	73	(170)
Accumulated Foreign Currency Adjustment Attributable to Noncontrolling Interest
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other Comprehensive Income (Loss), Net of Tax	(8)	0
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance – beginning of period, net of tax	(13)	(66)
Balance – end of period, net of tax	13	(92)
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	(8)	(17)
Net Realized Gains (Losses) Reclassified from AOCI	(41)	16
Other comprehensive income (loss), before income tax	33	(33)
Other Comprehensive Income (Loss), Tax	7	(7)
Other Comprehensive Income (Loss), Net of Tax	26	(26)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Noncontrolling Interest
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other Comprehensive Income (Loss), Net of Tax	0	0
Postretirement Benefit Liability Adjustment [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance – beginning of period, net of tax	297	225
Balance – end of period, net of tax	296	224
Accumulated Defined Benefit Plans Adjustment Including Portion Attributable to Noncontrolling Interest
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss), before income tax	(2)	0
Other Comprehensive Income (Loss), Tax	(1)	1
Other Comprehensive Income (Loss), Net of Tax	(1)	(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
Accumulated Other Comprehensive Income (Loss) [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance – beginning of period, net of tax	(6,809)	(10,185)
Other Comprehensive Income (Loss), Net of Tax	(577)	1,290
Balance – end of period, net of tax	$ (7,386)	$ (8,895)