Income Taxes - Summary of Deferred Tax Assets and Liabilities (Parenthetical) (Detail) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Schedule Of Deferred Tax Assets And Liabilities [Line Items]
Deferred tax assets	$ 1,111,000,000	$ 1,134,000,000
Other Assets [Member]
Schedule Of Deferred Tax Assets And Liabilities [Line Items]
Deferred tax assets	$ 37	$ 25

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319

Name:	us-gaap_DeferredTaxAssetsGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant