Acquisitions and Dispositions - Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Business Acquisition [Line Items]
Proceeds from sale of business	$ 22	$ 32
Nonhospital Health Care [Member]
Business Acquisition [Line Items]
Cash paid for acquisition	80	13
Hospitals [Member]
Business Acquisition [Line Items]
Cash paid for acquisition	15	14
Real Estate [Member]
Business Acquisition [Line Items]
Pretax gain (loss) on sales of business	4	32
Proceeds from sale of business	$ 22	$ 32