General and significant accounting policies (ASU 2018-12 Transition) (Details) - USD ($) $ in Millions			3 Months Ended		6 Months Ended
		Jan. 01, 2021	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reinsurance recoverable on losses and loss expenses	[1]		$ (18,398)		$ (18,398)		$ (18,859)
Reinsurance recoverable on policy benefits	[1]		(315)		(315)		(302)
Deferred policy acquisition costs			6,666		6,666		6,031
Value of business acquired			(3,575)		(3,575)		(3,702)
Prepaid reinsurance premiums			(3,599)		(3,599)		(3,136)
Investments in partially-owned insurance companies			(3,542)		(3,542)		(2,507)
Unpaid losses and loss expenses			(76,480)	$ (73,448)	(76,480)	$ (73,448)	(75,747)	$ (72,330)
Unearned premiums			(21,860)		(21,860)		(19,713)
Future policy benefits		$ 7,652	11,064	6,756	11,064	6,756	10,476
Market risk benefits			722		722		800
Insurance and reinsurance balances payable			(8,429)		(8,429)		(7,780)
Deferred tax liabilities			(533)		(533)		(377)
Retained earnings			(49,467)		(49,467)		(48,305)
Accumulated other comprehensive income (loss) (AOCI)			(9,822)		(9,822)		(10,185)
Net premiums written			(11,951)	(10,293)	(22,661)	(19,482)
Net premiums earned			(10,999)	(9,549)	(21,141)	(18,286)
Net realized (gains) losses			304	503	381	480
Market risk benefits gains (losses)			7	33	122	(16)
Losses and loss expenses			(5,683)	(5,206)	(10,831)	(9,770)
Policy benefits			(830)	(361)	(1,627)	(734)
Policy acquisition costs			(2,016)	(1,726)	(3,964)	(3,445)
Other (income) expense			(100)	101	(396)	(211)
Income Tax (Expense) Benefit			(392)	(291)	(776)	(644)
Net income (loss)			(1,793)	(1,190)	(3,685)	(3,143)
Current discount rate on future policy benefits			(35)	632	(186)	1,067
Instrument-specific credit risk on market risk benefits			11	17	8	40
Other Comprehensive Income (Loss), Tax			28	183	(104)	962
Comprehensive income (loss)			866	(3,073)	4,048	(4,449)
Net Cash Provided by (Used in) Operating Activities					4,766	5,166
Net Cash Provided by (Used in) Financing Activities					(2,312)	(725)
Liability for Future Policy Benefit, Remeasurement Gain (Loss)			5	0	4	6
Equity in net income of partially-owned entities	[2]		(120)	72	(460)	(291)
Increase (Decrease) in Deferred Income Taxes					43	108
Unpaid losses and loss expenses					561	1,949
Unearned premiums					1,913	1,554
Future policy benefits					351	99
Accounts payable, accrued expenses, and other liabilities					(388)	67
Reinsurance recoverable					455	(642)
Increase (Decrease) in Deferred Policy Acquisition Costs					(546)	(232)
Increase (Decrease) in Other Operating Assets and Liabilities, Net					39	(370)
Net cash flows used for investing activities					(2,262)	1,125
Segment Life [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net premiums written			(1,270)	(562)	(2,563)	(1,138)
Net premiums earned			(1,256)	(539)	(2,520)	(1,081)
Losses and loss expenses			(35)	(27)	(67)	(51)
Policy benefits			(705)	(298)	(1,417)	(609)
Policy acquisition costs			(277)	(138)	(550)	(271)
Other (income) expense			(26)	(12)	(41)	(42)
Overseas General Insurance [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net premiums written			(2,885)	(2,640)	(6,148)	(5,719)
Net premiums earned			(2,908)	(2,696)	(5,694)	(5,324)
Losses and loss expenses			(1,267)	(1,143)	(2,504)	(2,439)
Policy benefits			(137)	(81)	(247)	(174)
Policy acquisition costs			(746)	(697)	(1,459)	(1,376)
Other (income) expense			(10)	3	(19)	5
Term Life Insurance | Segment Life [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs			356	283	356	283	320	246
Future policy benefits		454	892	573	892	573
Policy acquisition costs					(49)	(36)
Whole Life Insurance | Segment Life [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs			456	336	456	336	395	334
Future policy benefits		3,767	4,947	3,101	4,947	3,101
Policy acquisition costs					(11)	(9)
Accident and Health Insurance Product Line [Member] | Segment Life [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs			1,081	740	1,081	740	902	745
Future policy benefits		2,569	4,242	2,222	4,242	2,222
Policy acquisition costs					(63)	(47)
Accident and Health Insurance Product Line [Member] | Overseas General Insurance [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Future policy benefits		773	751	748	751	748
Insurance, Other | Segment Life [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs			118	118	118	118	121	$ 108
Future policy benefits		89	$ 232	112	232	112
Policy acquisition costs					$ (10)	(10)
Variable Annuity
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Market risk benefits		1,163
Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reinsurance recoverable on losses and loss expenses							(18,901)
Reinsurance recoverable on policy benefits							(303)
Deferred policy acquisition costs							5,788
Value of business acquired							(3,596)
Prepaid reinsurance premiums							(3,140)
Investments in partially-owned insurance companies							(2,877)
Unpaid losses and loss expenses							(76,323)
Unearned premiums							(20,360)
Future policy benefits							10,120		$ 6,065	[3]
Market risk benefits							0
Insurance and reinsurance balances payable							(7,795)
Deferred tax liabilities							(292)
Retained earnings							(48,334)
Accumulated other comprehensive income (loss) (AOCI)							(10,193)
Net premiums written				(10,302)		(19,501)
Net premiums earned				(9,557)		(18,303)
Net realized (gains) losses				504		403
Market risk benefits gains (losses)				0		0
Losses and loss expenses				(5,408)		(10,195)
Policy benefits				(159)		(304)
Policy acquisition costs				(1,739)		(3,476)
Other (income) expense				101		(209)
Income Tax (Expense) Benefit				(293)		(648)
Net income (loss)				(1,215)		(3,189)
Current discount rate on future policy benefits				0		0
Instrument-specific credit risk on market risk benefits				0		0
Other Comprehensive Income (Loss), Tax				(245)		(1,057)
Comprehensive income (loss)				(3,656)		(5,436)
Net Cash Provided by (Used in) Operating Activities						5,160
Net Cash Provided by (Used in) Financing Activities						(719)
Previously Reported | Term Life Insurance | Segment Life [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Future policy benefits	[3]								391
Previously Reported | Whole Life Insurance | Segment Life [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Future policy benefits	[3]								2,578
Previously Reported | Accident and Health Insurance Product Line [Member] | Segment Life [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Future policy benefits	[3]								2,270
Previously Reported | Accident and Health Insurance Product Line [Member] | Overseas General Insurance [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Future policy benefits	[3]								754
Previously Reported | Insurance, Other | Segment Life [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Future policy benefits	[3]								72
Previously Reported | Variable Annuity
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Market risk benefits									$ 1,138
Effect of Modified Retrospective Application Accounting Standards Update 2018-12
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reinsurance recoverable on losses and loss expenses							(42)
Reinsurance recoverable on policy benefits							(1)
Deferred policy acquisition costs							243
Value of business acquired							(106)
Prepaid reinsurance premiums							(4)
Investments in partially-owned insurance companies							(370)
Unpaid losses and loss expenses							(576)
Unearned premiums							(647)
Future policy benefits							356
Market risk benefits							800
Insurance and reinsurance balances payable							(15)
Deferred tax liabilities							(85)
Retained earnings		(52)					(29)
Accumulated other comprehensive income (loss) (AOCI)		1,800					$ 8
Net premiums written				(9)		(19)
Net premiums earned				(8)		(17)
Net realized (gains) losses				1		(77)
Market risk benefits gains (losses)				(33)		16
Losses and loss expenses				(202)		(425)
Policy benefits				202		430
Policy acquisition costs				(13)		(31)
Other (income) expense				0		(2)
Income Tax (Expense) Benefit				(2)		(4)
Net income (loss)				(25)		(46)
Current discount rate on future policy benefits				632		1,067
Instrument-specific credit risk on market risk benefits				17		40
Other Comprehensive Income (Loss), Tax				62		95
Comprehensive income (loss)				$ 583		987
Net Cash Provided by (Used in) Operating Activities						6
Net Cash Provided by (Used in) Financing Activities						$ (6)
Liability for Future Policy Benefit, Remeasurement Gain (Loss)		1,587
AOCI, Market Risk Benefit, Instrument-Specific Credit Risk, before Tax		77
Effect of Modified Retrospective Application Accounting Standards Update 2018-12 | Term Life Insurance | Segment Life [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Liability for Future Policy Benefit, Remeasurement Gain (Loss)		63
Effect of Modified Retrospective Application Accounting Standards Update 2018-12 | Whole Life Insurance | Segment Life [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Liability for Future Policy Benefit, Remeasurement Gain (Loss)		1,189
Effect of Modified Retrospective Application Accounting Standards Update 2018-12 | Accident and Health Insurance Product Line [Member] | Segment Life [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Liability for Future Policy Benefit, Remeasurement Gain (Loss)		299
Effect of Modified Retrospective Application Accounting Standards Update 2018-12 | Accident and Health Insurance Product Line [Member] | Overseas General Insurance [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Liability for Future Policy Benefit, Remeasurement Gain (Loss)		19
Effect of Modified Retrospective Application Accounting Standards Update 2018-12 | Insurance, Other | Segment Life [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Liability for Future Policy Benefit, Remeasurement Gain (Loss)		17
Effect of Modified Retrospective Application Accounting Standards Update 2018-12 | Guaranteed Minimum Death Benefit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Market risk benefits gains (losses)		59
OCI, Market Risk Benefit, Instrument-Specific Credit Risk, Gain (Loss), before Adjustments and Tax	[4]	$ 84

[1] Net of valuation allowance for uncollectible reinsurance.

[2] Equity in net income (loss) of partially-owned entities includes mark-to-market gains (losses) on private equities where we own more than three percent of $(3) million and $239 million for the three and six months ended June 30, 2023, respectively, and $(134) million and $121 million, respectively, for the prior year periods. This line item also includes net income of $22 million and $36 million attributable to our investments in Huatai for the three and six months ended June 30, 2023, respectively, compared to $15 million and $55 million, respectively, for the prior year periods.

[3] Includes future policy benefits previously included within Unpaid losses on the pre-adoption consolidated balance sheets, primarily certain international A&H business, and excludes deferred profit liability and certain guaranteed minimum death benefits reclassified to Market risk benefits on the post adoption period balance sheets.

[4] Includes $77 million of instrument-specific credit risk allocated from retained earnings to AOCI.