Organization and Basis of Presentation - Additional Information (Detail) - USD ($)					2 Months Ended	3 Months Ended								12 Months Ended
	Mar. 03, 2017	Feb. 22, 2017	Aug. 04, 2016	Aug. 03, 2016	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Organization And Basis Of Presentation [Line Items]
Month and year of incorporation														2007-01
Common stock, shares issued						12,350,360				7,201,774				12,350,360	7,201,774
Repayment of principal and accrued interest														$ 4,500,000
Cash and cash equivalents						$ 9,007,071				$ 8,691,155				9,007,071	$ 8,691,155	$ 14,155,809
Net loss						(1,527,343)	$ (3,025,281)	$ (2,970,498)	$ (3,225,409)	(2,624,152)	$ (2,735,400)	$ (3,241,163)	$ (3,520,748)	(10,748,531)	(12,121,463)
Accumulated deficit						$ (58,809,143)				$ (48,060,612)				$ (58,809,143)	$ (48,060,612)
Scenario Forecast [Member]
Organization And Basis Of Presentation [Line Items]
Gross proceeds from public offering of common stock					$ 8,000,000
Square 1 Bank [Member] | Loan and security agreement [Member]
Organization And Basis Of Presentation [Line Items]
Repayment of principal and accrued interest			$ 4,500,000
Subsequent Event [Member]
Organization And Basis Of Presentation [Line Items]
Issuance of common stock from At-The-Market offering, shares net	362,068
July 2016 Financing and August 2016 Financing [Member]
Organization And Basis Of Presentation [Line Items]
Common stock, shares issued				5,048,632			5,048,632
Aggregate gross proceeds from sale of common stock and warrants				$ 14,500,000			$ 14,500,000
Underwritten Public Offering [Member] | Scenario Forecast [Member]
Organization And Basis Of Presentation [Line Items]
Issuance of common stock from At-The-Market offering, shares net					2,775,861
Gross proceeds from public offering of common stock					$ 8,000,000
Underwritten Public Offering [Member] | Subsequent Event [Member]
Organization And Basis Of Presentation [Line Items]
Issuance of common stock from At-The-Market offering, shares net		2,413,793
Gross proceeds from public offering of common stock	$ 8,000,000