Significant Accounting Policies - Narrative (Details) shares in Millions, person in Millions, patient in Millions, member in Millions		1 Months Ended	3 Months Ended					12 Months Ended
	Jul. 01, 2019 USD ($) store	Dec. 31, 2018 USD ($) shares	Sep. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) shares	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2019 USD ($) member person clinic patient store Segment state shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($)	Dec. 31, 2014	Jan. 01, 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
Number of people served | person								37
Number of reportable segments | Segment								4
Deferred acquisition costs		$ 22,000,000			$ 22,000,000			$ 271,000,000	$ 22,000,000
Depreciation								1,900,000,000	1,700,000,000	$ 1,700,000,000
Store rationalization charges								231,000,000	0	215,000,000
Impairment of long-lived assets								0	43,000,000	0
Goodwill impairments			$ 0					0	6,149,000,000	181,000,000
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		$ 2,100,000,000			2,100,000,000			$ 2,200,000,000	2,100,000,000
Self insurance liabilities		$ 865,000,000			$ 865,000,000			$ 856,000,000	865,000,000
Pharmacy rebate period								30 days
Health insurer fee								$ 0	157,000,000	0
Advertising costs								$ 396,000,000	364,000,000	230,000,000
Provisional benefit of revaluation of net DTL due to TCJA										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			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								32,000,000	45,000,000	35,000,000
Other revenues from transactions with related party								96,000,000	135,000,000	139,000,000
Charitable contribution to CVS Health Foundation								30,000,000
Increase to retained earnings		$ 40,911,000,000			$ 40,911,000,000			$ 45,108,000,000	40,911,000,000			$ 41,089,000,000
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								$ (154,000,000)	0	0
Other Insurance Liabilities
Significant Accounting Policies [Line Items]
Liability for unpaid claims		816,000,000			816,000,000			704,000,000	816,000,000
Future policy benefits		536,000,000			536,000,000			508,000,000	536,000,000
Other Long-Term Insurance Liabilities
Significant Accounting Policies [Line Items]
Liability for unpaid claims		1,900,000,000			1,900,000,000			1,800,000,000	1,900,000,000
Future policy benefits		$ 6,200,000,000			6,200,000,000			$ 5,600,000,000	6,200,000,000
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)		3.50%						3.50%
Interest rate for pension and annuity investment contracts		3.50%						3.50%
Share-based compensation arrangement, requisite service 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		13.40%						15.00%
Share-based compensation arrangement, requisite service 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 2016-02
Significant Accounting Policies [Line Items]
Increase to retained earnings												178,000,000
Increase to retained earnings, pre-tax												$ 241,000,000
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						215,000,000
Goodwill impairments									6,149,000,000	$ 181,000,000
Retail/ LTC | Brazil Subsidiary | Discontinued Operations, Disposed of by Sale
Significant Accounting Policies [Line Items]
Number of stores | store	50
Retail/ LTC | Long-Term Care Reporting Unit
Significant Accounting Policies [Line Items]
Goodwill impairments					2,200,000,000	$ 0	$ 3,900,000,000
Health Care Benefits
Significant Accounting Policies [Line Items]
Number of people served | person								37
Goodwill impairments									0
Health Insurance Product Line
Significant Accounting Policies [Line Items]
Premium deficiency reserve		$ 16,000,000			$ 16,000,000			$ 4,000,000	$ 16,000,000