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Related Party Transactions - Transactions with Significant Shareholders, their Affiliates and Other Related Parties (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Related Party Transactions [Abstract]      
Sales & other services   $ 1 $ 7
Other purchases $ 12 1 65
Accounts receivable 7 7 8
Accounts payable $ 51 $ 51 $ 61