Summary of significant accounting policies (Narrative) (Detail) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Jul. 01, 2022	Jan. 01, 2021
Summary of significant accounting policies [Line Items]
Deferred Marketing Costs, Amortization Period		10 years
Deferred Advertising Costs	$ 243	$ 243	$ 189
Deferred Policy Acquisition Costs, Amortization Expense		$ 7,392	6,918	$ 6,547
Recoverable from unrated reinsurers, ceded reserve, default factor (percent)		34.00%
Percentage of fair value of loaned securities		102.00%
Quality assessment threshold used in goodwill impairment testing		50.00%
Property, Plant and Equipment, Net	2,400	$ 2,400	2,000
Net operating results of ESIS included within Administrative expenses		12	25	18
Cigna integration expenses		48	0	0
Net income		5,313	8,539	3,533
Comprehensive Income (Loss), Net of Tax, Attributable to Parent		(5,230)	6,020	5,783
Deposit liabilities included in Deposit liabilities	70	70	74
Retained earnings	48,334	48,334	47,365
Accumulated other comprehensive income	(10,193)	(10,193)	350
Stockholders' Equity	(50,540)	(50,540)	(59,714)	(59,441)
Deposit Assets	96	96	101
Accounting Standards Update 2018-12 | Cumulative Effect, Period of Adoption, Adjustment [Member]
Summary of significant accounting policies [Line Items]
Stockholders' Equity						$ 1,800
Cigna's Life Insurance Business in Asian Markets
Summary of significant accounting policies [Line Items]
Net income	$ 148
Stockholders' Equity					$ (5,359)
Cigna's Life Insurance Business in Asian Markets | Debt Securities [Member]
Summary of significant accounting policies [Line Items]
Assets, Fair Value Adjustment		$ 211
Minimum
Summary of significant accounting policies [Line Items]
Reinsurance Premiums, Amortization Period		1 year
Debt Securities, Held-to-Maturity, Accrued Interest, Threshold Period, Writeoff	30 days	30 days
Liability for Future Policy Benefits, Interest Rate	1.00%	1.00%
Maximum
Summary of significant accounting policies [Line Items]
Reinsurance Premiums, Amortization Period		3 years
Affiliated notional cash pooling program	$ 300	$ 300
Finite-Lived Intangible Asset, Useful Life		25 years
Debt Securities, Held-to-Maturity, Accrued Interest, Threshold Period, Writeoff	45 days	45 days
Liability for Future Policy Benefits, Interest Rate	9.00%	9.00%
Selling and Marketing Expense [Member]
Summary of significant accounting policies [Line Items]
Deferred Policy Acquisition Costs, Amortization Expense		$ 121	85	$ 99
Fair Value Adjustment to Acquired Loss Reserves [Member] | The Chubb Corporation [Member]
Summary of significant accounting policies [Line Items]
Balance of FV adjustment on Unpaid Losses and Loss Expenses	$ 74	74	$ 90
Software Development [Member]
Summary of significant accounting policies [Line Items]
Property, Plant and Equipment, Net	1,600	$ 1,600
Property, Plant and Equipment, Useful Life		15 years
Software Development [Member] | Minimum
Summary of significant accounting policies [Line Items]
Property, Plant and Equipment, Useful Life		3 years
Software Development [Member] | Maximum
Summary of significant accounting policies [Line Items]
Property, Plant and Equipment, Useful Life		5 years
Building [Member]
Summary of significant accounting policies [Line Items]
Property, Plant and Equipment, Net	$ 253	$ 253
Building [Member] | Maximum
Summary of significant accounting policies [Line Items]
Property, Plant and Equipment, Useful Life		40 years