The total amount of sublease rental income recognized during the period that reduces the entity's rent expense incurred under operating leases.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 10
-Section 55
-Paragraph 40
-Subparagraph (Note 3)
-URI http://asc.fasb.org/extlink&oid=82846649&loc=d3e38371-112697

Name:	us-gaap_OperatingLeasesRentExpenseSubleaseRentals1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Commitments and Contingencies - Additional Information (Detail)		12 Months Ended
	Jul. 07, 2015 USD ($) ft²	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Commitments And Contingencies [Line Items]
Rent expense		$ 249,057	$ 253,316
California [Member] \| Sublease [Member]
Commitments And Contingencies [Line Items]
Area of subleased premises \| ft²	7,049
Monthly base rent payments	$ 19,737
Percentage of rent increase under sublease	3.00%