Segment Reporting - Reconciliation from Operating Income to Adjusted Operating Income (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue, Major Customer [Line Items]
Operating income (GAAP measure)		$ 4,326	$ 4,680	$ 7,903	$ 8,138
Amortization of intangible assets		582	578	1,169	1,164
Acquisition-related integration costs		40	70	81	139
Acquisition purchase price adjustment outside of measurement period		(61)	0	(61)	0
Adjusted operating income (loss)		$ 4,887	$ 5,328	$ 9,092	$ 9,441
Health Care Benefits
Revenue, Major Customer [Line Items]
Receipt related purchase price adjustment from acquisition	$ (61)