Segment Reporting - Reconciliation from Operating Income to Adjusted Operating Income (Details) $ in Millions	3 Months Ended
Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($) store
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Operating income (GAAP measure)	$ 3,458	$ 2,690
Amortization of intangible assets	586	622
Acquisition-related integration costs	69	148
Store rationalization charges	0	135
Adjusted operating income (loss)	$ 4,113	$ 3,595
Retail/ LTC
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Number of under performing stores \| store		46

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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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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