Property and Equipment - Additional Information (Detail) $ in Millions	9 Months Ended
Sep. 30, 2018 USD ($)
Furniture, fixtures and office equipment
Depreciation And Other Amortization Expenses [Line Items]
Amount of divestiture of long-lived	$ 0.5

Amount of divestiture of long-lived, physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

No definition available.

Name:	us-gaap_PropertyPlantAndEquipmentDisposals
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration