Acquisitions (Narrative) (Details) - USD ($) $ in Millions			3 Months Ended			12 Months Ended
	Jul. 01, 2023	Jul. 01, 2022	Mar. 31, 2024	Dec. 31, 2023		Dec. 31, 2023		Jun. 30, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Goodwill				$ 19,686	[1]	$ 19,686	[1]		$ 16,228	$ 15,213
Other intangible assets				6,775		6,775			5,441
Value of business acquired				3,674		3,674			3,702	$ 235	$ 263
Repurchase agreements				$ 2,833		$ 2,833			$ 1,419
Huatai Group [Member]
Business Acquisition [Line Items]
Subsidiary, Ownership Percentage, Parent	69.60%			76.50%		76.50%
Additional 7.0 percent ownership interest obtained in subsidiary				7.00%
Outstanding 1.9 percent additional ownership interest agreed on						0.60%
Huatai Group [Member] | Subsequent Event [Member]
Business Acquisition [Line Items]
Additional 7.7 percent ownership interest obtained in subsidiary			9.00%
Huatai Group [Member]
Business Acquisition [Line Items]
Ownership Percentage								64.20%
Cigna's Life Insurance Business in Asian Markets
Business Acquisition [Line Items]
Goodwill		$ 1,189
Other intangible assets		309
Value of business acquired		$ 3,633
Business Acquisition, Effective Date of Acquisition		Jul. 01, 2022
Payments to Acquire Businesses, Gross		$ 5,400
Repurchase agreements		$ 2,000
Huatai Group [Member]
Business Acquisition [Line Items]
Business Combination, Step Acquisition, Equity Interest in Acquiree, Fair Value	$ 4,100
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain	763
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Loss	17
Write-off of Accumulated AOCI Loss Balance, Equity Method Invesmtent	611
Business combination, Realized Gain (Loss) from Write-off of AOCI	(628)
Deposits previously paid on additional ownership interest obtained						$ 727
Deposits previously paid on additional ownership interest agreed on						12
Outstanding payment to be made on additional ownership interest agreed on				$ 24		$ 24
Goodwill	3,394
Other intangible assets	1,655
Value of business acquired	309
Repurchase agreements	$ 1,269
Huatai Group [Member] | Subsequent Event [Member]
Business Acquisition [Line Items]
Deposits previously paid on additional ownership interest obtained			$ 559
Payments to Acquire Business and Interest in Affiliates, Pending			221
Deposits previously paid on ownership obtained			319
Payments to Acquire Additional Interest in Subsidiaries			$ 338

[1] At December 31, 2023, Goodwill from Huatai Group includes approximately $759 million attributable to noncontrolling interests