Stock Incentive Plans - Stock-Based Compensation Expense and ESPP (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Nov. 28, 2018
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 453	$ 280	$ 234
Shares issued employee stock purchase plan (in shares)	2,000,000
Average purchase price of shares purchased (in dollars per share)	$ 53.29
Employee Stock Options and Stock Appreciation Rights
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 76	70	65
Compensation not yet recognized, period for recognition	2 years 1 month 6 days
Compensation not yet recognized, options	$ 41
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	$ 377	210	169
Compensation not yet recognized, other than options	$ 524
Compensation not yet recognized, period for recognition	2 years 2 months 12 days
Vested in period, fair value	$ 265	262	$ 175
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	30,000,000
Number of shares available for grant	7,000,000
Offering period	6 months
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	32,000,000
Number of shares available for grant	17,000,000
Aetna Inc 2010 Stock Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Number of shares available for grant	27,000,000			32,000,000
Capital shares reserved for future issuance				22,000,000