Segment and Geographic Information - Schedule Of Geographic Distributions Of Revenues, Salaries And Benefits, Supplies, Other Operating Expenses, Equity In Earnings Of Affiliates, Adjusted Segment EBITDA, Depreciation And Amortization, Assets And Goodwill And Other Intangible Assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Revenues	$ 70,603	$ 64,968	$ 60,233
Salaries and benefits	31,170	29,487	27,685
Supplies	10,755	9,902	9,371
Other operating expenses	14,819	12,875	11,155
Equity in (earnings) losses of affiliates	(23)	(22)	(45)
Depreciation and amortization	3,312	3,077	2,969
Interest expense	2,061	1,938	1,741
Losses (gains) on sales of facilities	(14)	5	(1,301)
Losses on retirement of debt	0	0	78
Income before income taxes	8,523	7,706	8,580
Assets	59,513	56,211	52,438
Goodwill and other intangible assets, Beginning Balance	9,945	9,653	9,540
Goodwill and other intangible assets, Acquisitions	170	362	262
Foreign Currency Translation Amortization And Other	(22)	(70)	(149)
Goodwill and other intangible assets, Ending Balance	10,093	9,945	9,653
Operating Segments [Member]
Segment Reporting Information [Line Items]
Adjusted segment EBITDA	15,133	13,700	12,599
Eliminations and Reconciling Items [Member]
Segment Reporting Information [Line Items]
Corporate and Other	1,251	974	532
Depreciation and amortization	3,312	3,077	2,969
Interest expense	2,061	1,938	1,741
Losses (gains) on sales of facilities	(14)	5	(1,301)
Losses on retirement of debt	0	0	(78)
Income before income taxes	8,523	7,706	8,580
National Group [Member]
Segment Reporting Information [Line Items]
Goodwill and other intangible assets, Beginning Balance	1,241	1,244	1,212
Goodwill and other intangible assets, Acquisitions	0	0	75
Foreign Currency Translation Amortization And Other	(4)	(3)	(43)
Goodwill and other intangible assets, Ending Balance	1,237	1,241	1,244
National Group [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	19,614	18,105	16,767
Salaries and benefits	7,483	7,196	6,959
Supplies	2,812	2,658	2,569
Other operating expenses	4,892	4,253	3,624
Equity in (earnings) losses of affiliates	2	(2)	(1)
Operating expenses	15,189	14,105	13,151
Adjusted segment EBITDA	4,425	4,000	3,616
Depreciation and amortization	857	834	801
Assets	12,855	12,487	11,793
Atlantic Group [Member]
Segment Reporting Information [Line Items]
Goodwill and other intangible assets, Beginning Balance	2,064	2,057	1,970
Goodwill and other intangible assets, Acquisitions	61	8	90
Foreign Currency Translation Amortization And Other	(1)	(1)	(3)
Goodwill and other intangible assets, Ending Balance	2,124	2,064	2,057
Atlantic Group [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	23,171	21,167	19,324
Salaries and benefits	8,525	8,058	7,752
Supplies	3,553	3,331	3,088
Other operating expenses	6,124	5,289	4,606
Equity in (earnings) losses of affiliates	(3)	(3)	(3)
Operating expenses	18,199	16,675	15,443
Adjusted segment EBITDA	4,972	4,492	3,881
Depreciation and amortization	1,061	989	921
Assets	17,168	16,098	15,092
American Group [Member]
Segment Reporting Information [Line Items]
Goodwill and other intangible assets, Beginning Balance	5,478	5,152	5,062
Goodwill and other intangible assets, Acquisitions	105	326	90
Foreign Currency Translation Amortization And Other	3	0	0
Goodwill and other intangible assets, Ending Balance	5,586	5,478	5,152
American Group [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	24,601	22,318	20,858
Salaries and benefits	8,529	8,080	7,757
Supplies	4,035	3,616	3,331
Other operating expenses	6,363	5,473	4,711
Equity in (earnings) losses of affiliates	(62)	(59)	(43)
Operating expenses	18,865	17,110	15,756
Adjusted segment EBITDA	5,736	5,208	5,102
Depreciation and amortization	1,083	971	937
Assets	20,714	19,786	17,934
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenues	3,217	3,378	3,284
Depreciation and amortization	311	283	310
Assets	8,776	7,840	7,619
Goodwill and other intangible assets, Beginning Balance	1,162	1,200	1,296
Goodwill and other intangible assets, Acquisitions	4	28	7
Foreign Currency Translation Amortization And Other	(20)	(66)	(103)
Goodwill and other intangible assets, Ending Balance	$ 1,146	$ 1,162	$ 1,200