Goodwill (Narrative) (Detail)	9 Months Ended
Sep. 30, 2017 ReportingUnit
Goodwill And Intangible Assets Disclosure [Abstract]
Number of reporting units	4

Number of reporting units tested for impairment of goodwill. A reporting unit is an operating segment or one level below an operating segment.

No definition available.

Name:	us-gaap_NumberOfReportingUnits
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration