Subsequent Event - Additional Information (Detail) - Sales Agreement [Member] - Subsequent Event [Member]	Oct. 12, 2018 USD ($)
Subsequent Event [Line Items]
Percentage of gross proceeds from common stock as sales agent cash commission	3.00%
Maximum [Member]
Subsequent Event [Line Items]
Proceeds from sales of common stock	$ 100,000,000

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3255-108585

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