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, 2025	Dec. 31, 2024	Dec. 31, 2023
Segment Reporting Information [Line Items]
Revenues	$ 75,600	$ 70,603	$ 64,968
Salaries and benefits	32,859	31,170	29,487
Supplies	11,367	10,755	9,902
Other operating expenses	15,886	14,819	12,875
Equity in (earnings) losses of affiliates	(78)	(23)	(22)
Depreciation and amortization	3,523	3,312	3,077
Interest expense	2,248	2,061	1,938
Losses (gains) on sales of facilities	(37)	(14)	5
Income before income taxes	9,832	8,523	7,706
Assets	60,720	59,513	56,211
Goodwill and other intangible assets, Beginning Balance	10,093	9,945	9,653
Goodwill and other intangible assets, Acquisitions	218	170	362
Foreign Currency Translation Amortization And Other	(18)	(22)	(70)
Goodwill and other intangible assets, Ending Balance	10,293	10,093	9,945
Operating Segments [Member]
Segment Reporting Information [Line Items]
Adjusted segment EBITDA	17,041	15,059	13,700
Eliminations and Reconciling Items [Member]
Segment Reporting Information [Line Items]
Corporate and Other	1,475	1,177	974
Depreciation and amortization	3,523	3,312	3,077
Interest expense	2,248	2,061	1,938
Losses (gains) on sales of facilities	(37)	(14)	5
Income before income taxes	9,832	8,523	7,706
National Group [Member]
Segment Reporting Information [Line Items]
Goodwill and other intangible assets, Beginning Balance	1,237	1,241	1,244
Goodwill and other intangible assets, Acquisitions	21	0	0
Foreign Currency Translation Amortization And Other	(24)	(4)	(3)
Goodwill and other intangible assets, Ending Balance	1,234	1,237	1,241
National Group [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	21,278	19,656	18,105
Salaries and benefits	7,812	7,542	7,196
Supplies	3,043	2,812	2,658
Other operating expenses	5,321	4,908	4,253
Equity in (earnings) losses of affiliates	(1)	2	(2)
Operating expenses	16,175	15,264	14,105
Adjusted segment EBITDA	5,103	4,392	4,000
Depreciation and amortization	905	857	834
Assets	13,596	12,855	12,487
Atlantic Group [Member]
Segment Reporting Information [Line Items]
Goodwill and other intangible assets, Beginning Balance	2,124	2,064	2,057
Goodwill and other intangible assets, Acquisitions	90	61	8
Foreign Currency Translation Amortization And Other	0	(1)	(1)
Goodwill and other intangible assets, Ending Balance	2,214	2,124	2,064
Atlantic Group [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	24,709	23,380	21,167
Salaries and benefits	9,023	8,686	8,058
Supplies	3,689	3,553	3,331
Other operating expenses	6,358	6,206	5,289
Equity in (earnings) losses of affiliates	(3)	(3)	(3)
Operating expenses	19,067	18,442	16,675
Adjusted segment EBITDA	5,642	4,938	4,492
Depreciation and amortization	1,122	1,061	989
Assets	17,945	17,168	16,098
American Group [Member]
Segment Reporting Information [Line Items]
Goodwill and other intangible assets, Beginning Balance	5,586	5,478	5,152
Goodwill and other intangible assets, Acquisitions	101	105	326
Foreign Currency Translation Amortization And Other	1	3	0
Goodwill and other intangible assets, Ending Balance	5,688	5,586	5,478
American Group [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	26,445	24,668	22,318
Salaries and benefits	8,992	8,599	8,080
Supplies	4,263	4,035	3,616
Other operating expenses	6,962	6,367	5,473
Equity in (earnings) losses of affiliates	(68)	(62)	(59)
Operating expenses	20,149	18,939	17,110
Adjusted segment EBITDA	6,296	5,729	5,208
Depreciation and amortization	1,131	1,083	971
Assets	21,217	20,714	19,786
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenues	3,168	2,899	3,378
Depreciation and amortization	365	311	283
Assets	7,962	8,776	7,840
Goodwill and other intangible assets, Beginning Balance	1,146	1,162	1,200
Goodwill and other intangible assets, Acquisitions	6	4	28
Foreign Currency Translation Amortization And Other	5	(20)	(66)
Goodwill and other intangible assets, Ending Balance	$ 1,157	$ 1,146	$ 1,162