Severance Charges - Additional Information (Detail)	Jun. 30, 2018 USD ($)	Aug. 01, 2017 USD ($) SeniorExecutive
Restructuring Cost and Reserve [Line Items]
Number of terminated senior executives \| SeniorExecutive		1
Senior Executive [Member]
Restructuring Cost and Reserve [Line Items]
Severance payable \| $	$ 0	$ 1,200,000

Liability for amount due employees, in addition to wages and any other money that employers owe employees, when their employment ends through a layoff or other termination. For example, a company may provide involuntarily terminated employees with a lump sum payment equal to one week's salary for every year of employment.

No definition available.

Name:	us-gaap_SupplementalUnemploymentBenefitsSeveranceBenefits
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant