Stock Incentive Plans - Stock-Based Compensation Expense and ESPP (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Nov. 28, 2018
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 400	$ 453	$ 280
Shares issued employee stock purchase plan (in shares)	3,000,000
Average purchase price of shares purchased (in dollars per share)	$ 53.85
Employee Stock Options and Stock Appreciation Rights
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 71	76	70
Compensation not yet recognized, period for recognition	1 year 9 months 18 days
Compensation not yet recognized, options	$ 45
Expected to vest (in shares)	10,000,000
Restricted Stock Units and Performance Share Units
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 329	377	210
Compensation not yet recognized, other than options	$ 493
Compensation not yet recognized, period for recognition	2 years 3 months 18 days
Vested in period, fair value	$ 229	$ 265	262
Stock Appreciation Rights (SARs)
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Award vesting period	3 years
Accelerated compensation cost			14
Expiration period	10 years
Restricted Stock
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Accelerated compensation cost			$ 27
Employee Stock Option
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Award vesting period	4 years
Employee Stock
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Number of shares authorized	60,000,000
Number of shares available for grant	34,000,000
Purchase price of common stock percent	90.00%
Minimum
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Award vesting period	3 years
Maximum
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Award vesting period	5 years
CVS Health 2017 Incentive Compensation Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Number of shares authorized	58,000,000
Number of shares available for grant	38,000,000
Aetna Inc 2010 Stock Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Number of shares available for grant				32,000,000
Capital shares reserved for future issuance (in shares)				22,000,000