Organization and Business - Additional Information (Detail)	12 Months Ended
Dec. 31, 2017 Acquisition
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Number of acquisitions	2

The number of businesses acquired by the entity during the period.

No definition available.

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