Acquisitions and Dispositions - Additional Information (Detail) $ in Millions	3 Months Ended
Mar. 31, 2019 USD ($) Hospital	Mar. 31, 2018 USD ($)
Business Acquisition [Line Items]
Number of hospitals purchased \| Hospital	7
Proceeds from sale of business	$ 30	$ 767
Real Estate and Other Investments [Member]
Business Acquisition [Line Items]
Proceeds from sale of business	5	9
Pretax gain (loss) on sales of business		29
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		376
Hospitals [Member]
Business Acquisition [Line Items]
Aggregate purchase price	1,398	360
Non hospital Health Care [Member]
Business Acquisition [Line Items]
Aggregate purchase price	76	$ 19
Other [Member]
Business Acquisition [Line Items]
Goodwill	$ 207

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