Basis of Presentation and Significant Accounting Policies - Additional Information (Detail)	Sep. 30, 2017 Country
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Number of countries	20

The number of countries in which the entity operates as of balance sheet date.

No definition available.

Name:	us-gaap_NumberOfCountriesInWhichEntityOperates
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant