Segment Reporting - Reconciliation from Operating Income to Adjusted Operating Income (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($) store	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Operating income (GAAP measure)	$ 4,680	$ 3,332	$ 8,138	$ 6,022
Amortization of intangible assets	578	593	1,164	1,215
Acquisition-related integration costs	70	106	139	254
Store rationalization charges	0	0	0	135
Adjusted operating income (loss)	$ 5,328	$ 4,031	$ 9,441	$ 7,626
Retail/ LTC
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Number of under performing stores | store		46