Significant Accounting Policies - Narrative (Details) shares in Millions, people in Millions, member in Millions			3 Months Ended		12 Months Ended
	Oct. 22, 2020 USD ($)	Jul. 01, 2019 USD ($) store	Sep. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2020 USD ($) store people Segment member clinic patient state shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2014	Jan. 01, 2020 USD ($)	Aug. 31, 2019 USD ($)	Oct. 31, 2014 payment
Significant Accounting Policies [Line Items]
Number of plan members | member					105
Number of patients served per year | patient					1,000,000
Number of people served | people					34
Number of reportable segments | Segment					4
Deferred acquisition costs					$ 546,000,000	$ 271,000,000
Depreciation					2,100,000,000	1,900,000,000	$ 1,700,000,000
Store rationalization charges					0	231,000,000	0
Impairment of long-lived assets					0	0	43,000,000
Goodwill impairments					0	0	6,149,000,000
Impairment of intangible assets, indefinite-lived					$ 0	$ 0	0
Assumed interest rates on long-duration group life and long-term care contracts					5.10%	5.10%
HSA balances					$ 2,700,000,000	$ 2,200,000,000
Self insurance liabilities					927,000,000	856,000,000
Retained earnings					$ (49,640,000,000)	(45,108,000,000)
Pharmacy rebate period					30 days
Health insurer fee					$ 1,000,000,000.0	0	157,000,000
Advertising costs					$ 461,000,000	$ 396,000,000	364,000,000
TCJA tax expense (benefit)								$ 1,500,000,000
Benefit of revaluation of net DTL due to TCJA							100,000,000
Common stock, shares held in trust (in shares) | shares					1	1
VIE, ownership percentage									50.00%
Initial contractual term					10 years
Number of quarterly payments from VIE | payment												39
Proceeds from VIE					$ 183,000,000	$ 183,000,000	183,000,000
Expenses from transactions with related party					56,000,000	32,000,000	45,000,000
Other revenues from transactions with related party					77,000,000	96,000,000	135,000,000
Charitable contribution to CVS Health Foundation					50,000,000	30,000,000
Pre-tax income recognized					9,770,000,000	8,997,000,000	1,406,000,000
U.S. Department of Health and Human Services, ACA Risk Corridor Receivables [Member] | Settled Litigation
Significant Accounting Policies [Line Items]
Gain contingency, unrecorded amount											$ 313,000,000
Amount awarded from other party	$ 313,000,000
Former gain contingency, recognized in current period, before tax					307,000,000
Former gain contingency, recognized in current period, net of tax					$ 223,000,000
Heartland Healthcare Services
Significant Accounting Policies [Line Items]
Number of states in which entity operates | state					4
Foreign currency translation adjustments
Significant Accounting Policies [Line Items]
Cumulative translation adjustment from AOCI eliminated upon divestiture					$ 0	(154,000,000)	0
Other Insurance Liabilities
Significant Accounting Policies [Line Items]
Liability for unpaid claims					532,000,000	704,000,000
Future policy benefits					462,000,000	508,000,000
Other Long-Term Insurance Liabilities
Significant Accounting Policies [Line Items]
Liability for unpaid claims					1,500,000,000	1,800,000,000
Future policy benefits					$ 5,500,000,000	$ 5,600,000,000
Minimum
Significant Accounting Policies [Line Items]
Period after date of service a claim is paid					6 months
Assumed interest rates on limited payment pension contracts on large case pension business (in hundredths)					3.30%	3.50%
Interest rate for pension and annuity investment contracts					4.10%	3.50%
Award vesting period					3 years
Minimum | Building, building improvements and leasehold improvements
Significant Accounting Policies [Line Items]
Useful life of property plant and equipment					1 year
Minimum | Fixtures, equipment and internally developed software
Significant Accounting Policies [Line Items]
Useful life of property plant and equipment					3 years
Maximum
Significant Accounting Policies [Line Items]
Lease renewal term					5 years
Period after date of service a claim is paid					48 months
Assumed interest rates on limited payment pension contracts on large case pension business (in hundredths)					11.30%	11.30%
Interest rate for pension and annuity investment contracts					5.10%	5.20%
Award vesting period					5 years
Maximum | Building, building improvements and leasehold improvements
Significant Accounting Policies [Line Items]
Useful life of property plant and equipment					40 years
Maximum | Fixtures, equipment and internally developed software
Significant Accounting Policies [Line Items]
Useful life of property plant and equipment					10 years
ASU 2016-13 | Cumulative Effect, Period of Adoption, Adjustment
Significant Accounting Policies [Line Items]
Retained earnings										$ (3,000,000)
Brazil Subsidiary | Discontinued Operations, Disposed of by Sale | Foreign currency translation adjustments
Significant Accounting Policies [Line Items]
Cumulative translation adjustment from AOCI eliminated upon divestiture		$ 154,000,000
Retail/ LTC
Significant Accounting Policies [Line Items]
Number of stores | store					9,900
Number of walk-in medical clinics | clinic					1,100
Store rationalization charges			$ 96,000,000	$ 135,000,000
Goodwill impairments							6,149,000,000
Retail/ LTC | Brazil Subsidiary | Discontinued Operations, Disposed of by Sale
Significant Accounting Policies [Line Items]
Number of stores | store		50
Health Insurance Product Line
Significant Accounting Policies [Line Items]
Premium deficiency reserve					$ 11,000,000	$ 4,000,000	$ 16,000,000