Segment and Geographic Area Information - Schedule of Segment Reporting Information to Consolidated Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Assets By Segment [Line Items]
Total assets	$ 18,718	$ 20,038
Cash and cash equivalents	2,150	1,863	$ 1,919	$ 1,877
Corporate goodwill	4,535	5,148	$ 5,249
Corporate fixed assets, net	5,594	5,499
LIFO reserve	481	371
Investment in common stock of Alcoa Corporation	0	1,020
Operating Segments
Schedule Of Assets By Segment [Line Items]
Total assets	15,499	15,415
Other
Schedule Of Assets By Segment [Line Items]
Cash and cash equivalents	2,150	1,863
Deferred income taxes	743	1,234
Corporate goodwill	333	331
Corporate fixed assets, net	310	308
LIFO reserve	(481)	(371)
Fair value of derivative contracts	91	24
Investment in common stock of Alcoa Corporation	0	1,020
Other	$ 73	$ 214