General and significant accounting policies (ASU 2018-12 Transition) (Details) - USD ($) $ in Millions			12 Months Ended
		Jan. 01, 2021	Dec. 31, 2023		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]		$ (19,952)		$ (18,859)
Reinsurance Recoverable Future Policy Benefits	[1]		(280)		(302)
Deferred policy acquisition costs			7,152		6,031
Value of business acquired			(3,674)		(3,702)	$ (235)	$ (263)
Goodwill			19,686	[2]	16,228	15,213
Prepaid Reinsurance Premiums			(3,221)		(3,136)
Investments in partially-owned insurance companies			(191)		(2,507)
Liability for Claims and Claims Adjustment Expense			(80,122)		(75,747)	(72,330)	(67,192)
Unearned Premiums			(22,051)		(19,713)
Future policy benefits		$ 7,652	13,888		10,476	7,837
Market risk benefits			771		800
Reinsurance Payable			(8,302)		(7,780)
Deferred tax liabilities			(1,555)		(377)
Retained earnings			(54,810)		(48,305)
Accumulated other comprehensive income			(6,809)		(10,185)
Premiums Written, Net			(47,361)		(41,720)	(37,827)
Premiums Earned, Net			(45,712)		(40,360)	(36,292)
Realized Investment Gains (Losses)			607		1,085	(1,030)
Market Risk Benefit, Change in Fair Value, Gain (Loss)			307		(80)	(91)
Policyholder Benefits and Claims Incurred, Net			(24,100)		(22,572)	(21,030)
Policy benefits			(3,628)		(2,314)	(1,740)
Policy acquisition costs			(8,259)		(7,339)	(6,758)
Other (income) expense			(836)		89	(2,367)
Income Tax Expense (Benefit)			(511)		(1,239)	(1,269)
Net income (loss)			(9,028)		(5,246)	(8,525)
Current discount rate on future policy benefits			84		1,480	387
Instrument-specific credit risk on market risk benefits			2		33	27
Other Comprehensive Income (Loss), Tax			(317)		965	366
Comprehensive income (loss)			12,376		(3,865)	6,384
Comprehensive Income (Loss), Net of Tax, Attributable to Parent			12,404		(3,865)	6,384
Net Cash Provided by (Used in) Operating Activities, Total			12,632		11,258	11,151
Net Cash Provided by (Used in) Financing Activities			(4,489)		(5,142)	(4,411)
Liability for Future Policy Benefit, Remeasurement Gain (Loss)			19		3	0
Equity in net income of subsidiaries and affiliates			(867)		(1)	(2,435)
Increase (Decrease) in Deferred Income Taxes			(1,124)		318	(84)
Unpaid losses and loss expenses			3,470		4,259	5,178
Unearned premiums			1,377		1,435	1,252
Future policy benefits			848		333	1,040
Accounts payable, accrued expenses, and other liabilities			(735)		(68)	(2,423)
Reinsurance recoverable			(498)		(1,737)	(1,949)
Increase (Decrease) in Deferred Policy Acquisition Costs			(1,100)		(396)	(422)
Increase (Decrease) in Other Operating Assets and Liabilities, Net			1,819		789	3,325
Net cash flows used for investing activities			(7,648)		(5,654)	(6,659)
Life Insurance [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Goodwill			4,742	[2]	1,943	843
Future policy benefits			12,679		9,326	6,685
Premiums Written, Net			(5,465)		(3,608)	(2,436)
Premiums Earned, Net			(5,398)		(3,510)	(2,339)
Policyholder Benefits and Claims Incurred, Net			(114)		(85)	(150)
Policy benefits			(3,216)		(1,998)	(1,388)
Policy acquisition costs			(1,089)		(785)	(552)
Other (income) expense			(115)		(30)	(108)
Overseas General Insurance [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Goodwill			5,262	[2]	4,605	4,653
Premiums Written, Net			(12,575)		(11,060)	(10,713)
Premiums Earned, Net			(12,231)		(10,803)	(10,441)
Policyholder Benefits and Claims Incurred, Net			(5,643)		(4,894)	(4,783)
Policy benefits			(457)		(358)	(360)
Policy acquisition costs			(3,113)		(2,818)	(2,799)
Other (income) expense			(25)		2	0
Term Life Insurance | Life Insurance [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs			402		324	250	125
Future policy benefits		454	931		716	538
Policy acquisition costs			(100)		(81)	(47)
Whole Life Insurance | Life Insurance [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs			534		392	330	299
Future policy benefits		3,767	6,917		3,919	3,537
Policy acquisition costs			(23)		(18)	(18)
Accident and Health [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Premiums Earned, Net			(6,233)		(4,892)	(3,809)
Accident and Health [Member] | Life Insurance [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs			1,301		891	730	733
Future policy benefits		2,569	4,383		4,453	2,509
Policy acquisition costs			(137)		(93)	(98)
Accident and Health [Member] | Overseas General Insurance [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Future policy benefits		773
Insurance, Other [Member] | Life Insurance [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs			274		268	263	220
Future policy benefits		89	448		238	101
Policy acquisition costs			$ (29)		(31)	(26)
Variable Annuity [Member]
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 Future 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)
Liability for Claims and Claims Adjustment Expense					(76,323)
Unearned Premiums					(20,360)
Future policy benefits					10,120		6,065	[3]
Market risk benefits					0
Reinsurance Payable					(7,795)
Deferred tax liabilities					(292)
Retained earnings					(48,334)
Accumulated other comprehensive income					(10,193)
Premiums Written, Net					(41,755)	(37,868)
Premiums Earned, Net					(40,389)	(36,355)
Realized Investment Gains (Losses)					965	(1,152)
Market Risk Benefit, Change in Fair Value, Gain (Loss)					0	0
Policyholder Benefits and Claims Incurred, Net					(23,342)	(21,980)
Policy benefits					(1,492)	(699)
Policy acquisition costs					(7,392)	(6,918)
Other (income) expense					74	(2,365)
Income Tax Expense (Benefit)					(1,255)	(1,277)
Net income (loss)					(5,313)	(8,539)
Current discount rate on future policy benefits					0	0
Instrument-specific credit risk on market risk benefits					0	0
Other Comprehensive Income (Loss), Tax					(1,121)	(427)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent					(5,230)	6,020
Net Cash Provided by (Used in) Operating Activities, Total					11,243	11,149
Net Cash Provided by (Used in) Financing Activities					(5,127)	(4,409)
Previously Reported | Term Life Insurance | Life Insurance [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Future policy benefits	[3]						391
Previously Reported | Whole Life Insurance | Life Insurance [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Future policy benefits	[3]						2,578
Previously Reported | Accident and Health [Member] | Life Insurance [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Future policy benefits	[3]						2,270
Previously Reported | Accident and Health [Member] | Overseas General Insurance [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Future policy benefits	[3]						754
Previously Reported | Insurance, Other [Member] | Life Insurance [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Future policy benefits	[3]						72
Previously Reported | Variable Annuity [Member]
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 Future Policy Benefits					(1)
Deferred policy acquisition costs					243
Value of business acquired					(106)
Prepaid Reinsurance Premiums					(4)
Investments in partially-owned insurance companies					(370)
Liability for Claims and Claims Adjustment Expense					(576)
Unearned Premiums					(647)
Future policy benefits					356
Market risk benefits					800
Reinsurance Payable					(15)
Deferred tax liabilities					(85)
Retained earnings		(52)			(29)
Accumulated other comprehensive income		1,800			8
Premiums Written, Net					(35)	(41)
Premiums Earned, Net					(29)	(63)
Realized Investment Gains (Losses)					(120)	(122)
Market Risk Benefit, Change in Fair Value, Gain (Loss)					80	91
Policyholder Benefits and Claims Incurred, Net					(770)	(950)
Policy benefits					822	1,041
Policy acquisition costs					(53)	(160)
Other (income) expense					15	(2)
Income Tax Expense (Benefit)					(16)	(8)
Net income (loss)					(67)	(14)
Current discount rate on future policy benefits					1,480	387
Instrument-specific credit risk on market risk benefits					33	27
Other Comprehensive Income (Loss), Tax					156	61
Comprehensive Income (Loss), Net of Tax, Attributable to Parent					1,365	364
Net Cash Provided by (Used in) Operating Activities, Total					15	2
Net Cash Provided by (Used in) Financing Activities					$ (15)	$ (2)
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 | Life Insurance [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 | Life Insurance [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 [Member] | Life Insurance [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 [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 [Member] | Life Insurance [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 Benefit, Change in Fair Value, Gain (Loss)		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] At December 31, 2023, Goodwill from Huatai Group includes approximately $759 million attributable to noncontrolling interests

[3] Includes future policy benefits previously included within Unpaid losses and loss expenses 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.