Segment Information (Reconciliation of Adjusted EBITDA from Segment to Consolidated Statements) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting [Abstract]
Adjusted EBITDA	$ 8,927	$ 7,927	$ 17,339	$ 16,057
Adjustments	(36)	(16)	(48)	(30)
Depreciation	(2,113)	(2,099)	(4,231)	(4,206)
Amortization	(1,270)	(1,165)	(2,514)	(2,322)
Interest expense	(1,093)	(1,112)	(2,112)	(2,324)
Investment and other income (loss), net	1,216	420	1,607	(296)
Income before income taxes	$ 5,630	$ 3,955	$ 10,042	$ 6,879