Segment Reporting - Reconciliation from Operating Income to Adjusted Operating Income (Details) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) store	Jun. 30, 2018 USD ($)
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Operating income (loss) (GAAP measure)	$ 3,332	$ (1,373)	$ 6,022	$ 623
Amortization of intangible assets	593	214	1,215	424
Acquisition-related transaction and integration costs	106	39	254	82
Store rationalization charges	0	0	135	0
Goodwill impairment	0	3,921	0	3,921
Loss on divestiture of subsidiary	0	0	0	86
Interest income on financing for the Aetna Acquisition	0	(202)	0	(244)
Adjusted operating income (loss)	$ 4,031	$ 2,599	7,626	4,892
Retail Long-Term Care Segment
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Store rationalization charges			$ 135
Loss on divestiture of subsidiary				$ (725)
Number of under performing stores \| store			46

Adjusted Operating Income (Loss)

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Number of Under Performing Stores

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Store Rationalization Charges

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The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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- Definition

Costs incurred to effect a business combination which have been expensed during the period. Such costs could include business integration costs, systems integration and conversion costs, and severance and other employee-related costs.

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Amount of gain (loss) from sale and disposal of integrated set of activities and assets capable of being conducted and managed for purpose of providing return in form of dividend, lower cost, or other economic benefit to investor, owner, member and participant.

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Total loss recognized during the period from the impairment of goodwill plus the loss recognized in the period resulting from the impairment of the carrying amount of intangible assets, other than goodwill.

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The net amount of operating interest income (expense).

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The net result for the period of deducting operating expenses from operating revenues.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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