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Summary of Significant Accounting Policies - Schedule of Supplemental Cash Flow Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Accounting Policies [Abstract]      
Interest, net of capitalized interest and periodic settlements from interest rate swap agreements $ 375 $ 384 $ 461
Income taxes $ 442 $ 419 $ 758