Business and Basis of Presentation - Additional Information (Detail)	6 Months Ended
Jun. 30, 2018 Segment
Organization Consolidation And Presentation Of Financial Statements [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