Acquisitions and Dispositions - Additional Information (Detail) $ in Millions	9 Months Ended
Sep. 30, 2019 USD ($) Hospital	Sep. 30, 2018 USD ($) Hospital
Business Acquisition [Line Items]
Number of hospitals purchased \| Hospital	7	2
Proceeds from sale of business	$ 49	$ 802
Real Estate and Other Investments [Member]
Business Acquisition [Line Items]
Proceeds from sale of business	24	44
Pretax gain (loss) on sales of business	18	48
Real Estate and Other Investments [Member] \| Louisiana Markets [Member]
Business Acquisition [Line Items]
Pretax gain (loss) on sales of business	(1)
Discontinued Operations, Disposed of by Sale [Member] \| Louisiana Markets [Member]
Business Acquisition [Line Items]
Proceeds from sale of business	25
Discontinued Operations, Disposed of by Sale [Member] \| Oklahoma [Member]
Business Acquisition [Line Items]
Proceeds from sale of business		758
Pretax gain (loss) on sales of business		372
Hospitals [Member]
Business Acquisition [Line Items]
Aggregate purchase price	1,399	788
Non hospital Health Care [Member]
Business Acquisition [Line Items]
Aggregate purchase price	193	$ 268
Other [Member]
Business Acquisition [Line Items]
Goodwill	$ 231

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