Acquisitions and Divestitures - Schedule of Acquired Assets and Liabilities Assumed (Detail) - USD ($) $ in Millions		1 Months Ended
	Jun. 13, 2017	Feb. 28, 2017	Jul. 31, 2016	Sep. 30, 2018	Dec. 31, 2017
Assets acquired:
Goodwill				$ 29,200	$ 29,172
Yahoo! Inc.
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Cash payment to Yahoo’s equity holders	$ 4,673
Estimated liabilities to be paid	38
Total consideration	4,711	$ 4,480	$ 4,830
Assets acquired:
Goodwill	2,144
Intangible assets subject to amortization	1,874
Property, plant, and equipment	1,799
Other	1,460
Total assets acquired	7,277
Liabilities assumed:
Total liabilities assumed	2,516
Net assets acquired:	4,761
Noncontrolling interest	(50)
Total consideration	$ 4,711