Cash Flow Information - Schedule of Cash Paid for Acquisitions Including Non-Controlling Interest (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplemental Cash Flow Information [Abstract]
Assets acquired	$ 0	$ 0	$ 2,003
Liabilities assumed	0	0	(868)
Equity issued	0	0	(870)
Working capital adjustment	0	(10)	0
Increase in Arconic’s shareholders’ equity	0	0	(60)
Cash paid	0	(10)	205
Less: cash acquired	0	0	302
Net cash paid	$ 0	$ (10)	$ (97)