Subsequent Events - Additional Information (Detail) - 2017 Private Placement - Subsequent Event $ in Millions	1 Months Ended
Oct. 31, 2017 USD ($) Agreement shares
Subsequent Event [Line Items]
Proceeds from private placement of common stock \| $	$ 50.0
Number of securities purchase agreements \| Agreement	2
Common Stock
Subsequent Event [Line Items]
Private placement of common stock shares \| shares	8,382,643

The cash inflow from the additional capital contribution to the entity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3255-108585

Name:	us-gaap_ProceedsFromIssuanceOfCommonStock
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration