Related-party Transactions - Schedule of Amounts Related to Receivable and Payable Balances with Related Parties (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Related Party Transactions [Abstract]
Receivables	$ 25	$ 54
Payables	$ 49	$ 77

For an unclassified balance sheet, amount of receivables arising from transactions with related parties.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
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-Subparagraph (SX 210.4-08(k)(1))
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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Name:	us-gaap_AccountsReceivableRelatedParties
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant