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Acquisitions and Investments - Summary of Acquisitions (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Business Combinations [Abstract]      
Fair value of assets acquired, net of cash acquired $ 154 $ 357 $ 116
Cash paid, net of cash acquired (86) (230) (86)
Liabilities assumed, debt issued and noncontrolling interest 68 127 30
Excess purchase price over fair value of net assets acquired $ 89 $ 74 $ 51