Significant Accounting Policies (Narrative) (Detail) $ in Millions	3 Months Ended
Sep. 30, 2018 USD ($)
Accounting Policy [Line Items]
Out of Period Adjustment	$ 6
Second Quarter 2018 Reporting Period [Member]
Accounting Policy [Line Items]
Out of Period Adjustment	3
First Quarter 2017 Reporting Period [Member]
Accounting Policy [Line Items]
Out of Period Adjustment	$ 3

Amount of each individual error being corrected in the correcting adjustment.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 1.N)
-URI http://asc.fasb.org/extlink&oid=26874127&loc=d3e30840-122693

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration