Acquisitions and Divestitures - Additional Information - 2015 Activity - Transaction, Reorganization, and Separation Costs (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Business Combinations [Abstract]
Transaction, reorganization, and separation costs	$ 66	$ 14	$ 120	$ 32