Segment and Geographic Information - Schedule of Geographic Distributions of Revenues, Equity in Earnings of Affiliates, Adjusted Segment EBITDA, Depreciation and Amortization and Assets (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Segment Reporting Information [Line Items]
Revenues	$ 14,820	$ 14,435	$ 29,765	$ 28,412
Equity in earnings of affiliates	(8)	(22)	(19)	(43)
Adjusted segment EBITDA	3,042	3,219	5,986	6,271
Depreciation and amortization	738	712	1,470	1,409
Interest expense	434	386	842	770
Losses (gains) on sales of facilities	32	(8)	22	(10)
Losses on retirement of debt	78	12	78	12
Income before income taxes	1,760	2,117	3,574	4,090
National Group [Member]
Segment Reporting Information [Line Items]
Revenues	7,349	7,300	14,855	14,356
Equity in earnings of affiliates	(1)	(9)	(2)	(16)
Adjusted segment EBITDA	1,540	1,845	3,106	3,550
Depreciation and amortization	364	339	719	662
American Group [Member]
Segment Reporting Information [Line Items]
Revenues	6,657	6,504	13,273	12,795
Equity in earnings of affiliates	(9)	(12)	(18)	(24)
Adjusted segment EBITDA	1,542	1,593	3,028	3,094
Depreciation and amortization	304	296	605	589
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenues	814	631	1,637	1,261
Equity in earnings of affiliates	2	(1)	1	(3)
Adjusted segment EBITDA	(40)	(219)	(148)	(373)
Depreciation and amortization	$ 70	$ 77	$ 146	$ 158