Acquisitions and Dispositions - Additional Information (Detail) $ in Millions	6 Months Ended
Jun. 30, 2019 USD ($) Hospital	Jun. 30, 2018 USD ($)
Business Acquisition [Line Items]
Number of hospitals purchased \| Hospital	7
Proceeds from sale of business	$ 41	$ 799
Real Estate and Other Investments [Member]
Business Acquisition [Line Items]
Proceeds from sale of business	16	41
Pretax gain (loss) on sales of business	18	42
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	1,397	360
Non hospital Health Care [Member]
Business Acquisition [Line Items]
Aggregate purchase price	107	$ 178
Other [Member]
Business Acquisition [Line Items]
Goodwill	$ 201

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