Stock Incentive Plans - Stock-Based Compensation Expense (Details) - USD ($) $ in Millions	8 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense			$ 588	$ 447	$ 484
Oak Street Health Inc.
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 71
Signify Health, Inc.
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense		$ 72
Restricted stock units and performance stock units
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense			497	369	404
Stock options and stock appreciation rights (“SARs”)
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense			$ 91	$ 78	$ 80