Acquisitions and Dispositions - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) Hospital	Dec. 31, 2019 USD ($) Hospital	Dec. 31, 2018 USD ($) Hospital
Business Acquisition [Line Items]
Number of hospitals purchased | Hospital	1	7	2
Proceeds from sale of business	$ 68	$ 61	$ 808
Real Estate and Other Investments [Member]
Business Acquisition [Line Items]
Pretax gain (loss) before tax			75
Pretax gain (loss) after tax			59
Proceeds from sale of business			50
Discontinued Operations, Disposed of by Sale [Member] | Oklahoma [Member]
Business Acquisition [Line Items]
Pretax gain (loss) before tax			353
Pretax gain (loss) after tax			265
Proceeds from sale of business			$ 758
Number of hospitals sold | Hospital			2
Discontinued Operations, Disposed of by Sale [Member] | Louisiana [Member]
Business Acquisition [Line Items]
Pretax gain (loss) before tax		18
Pretax gain (loss) after tax		13
Proceeds from sale of business		$ 61
Number of hospitals sold | Hospital		1
Discontinued Operations, Disposed of by Sale [Member] | Mississippi [Member]
Business Acquisition [Line Items]
Pretax gain (loss) before tax	(7)
Pretax gain (loss) after tax	(9)
Proceeds from sale of business	$ 68
Number of hospitals sold | Hospital	1
Hospitals [Member]
Business Acquisition [Line Items]
Aggregate purchase price		$ 1,384	$ 792
Nonhospital Health Care [Member]
Business Acquisition [Line Items]
Aggregate purchase price		298	461
Other [Member]
Business Acquisition [Line Items]
Goodwill	$ 279	$ 332	$ 636
Hospital and other nonhospital health care entities [Member]
Business Acquisition [Line Items]
Aggregate purchase price	$ 568