Summary of Significant Accounting Policies - Additional Information (Detail)						1 Months Ended			12 Months Ended
	Sep. 14, 2016 USD ($) $ / shares shares	Jan. 12, 2016 USD ($) $ / shares shares	Apr. 20, 2015 USD ($) $ / shares shares	Jul. 23, 2014 USD ($) $ / shares shares	Jul. 02, 2014	May 31, 2016 ft²	Jan. 31, 2016 USD ($)	Apr. 30, 2015 USD ($)	Dec. 31, 2016 USD ($) ft²	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Restricted cash deposit									$ 564,000	$ 39,000
Payment of offering costs				$ 2,300,000			$ 600,000	$ 500,000	$ 599,000	584,000	$ 2,285,000
Deferred offering costs										200,000
Issuance of common stock, shares | shares	5,062,892	3,157,894	2,628,571
Common stock price per share | $ / shares	$ 39.75	$ 47.50	$ 52.50
Reverse stock split description									In connection with preparing for the IPO, the Company’s board of directors and stockholders approved a 1-for-3.15 reverse stock split of the Company’s common stock
Reverse stock split effective date									Jul. 02, 2014
Reverse stock split ratio					0.3175
Issuance of additional shares of common stock upon conversion | shares				18,007,575
Proceeds from public offering of common stock, net of commissions and underwriting discounts and estimated offering costs	$ 189,200,000	$ 140,400,000	$ 129,100,000
Initial Public Offering [Member]
Summary Of Significant Accounting Policies [Line Items]
Issuance of common stock, shares | shares				5,750,000
Common stock price per share | $ / shares				$ 18.00
Proceeds from initial public offering of common stock, net of commissions and underwriting discounts				$ 94,000,000
ASU 2015-17, Balance Sheet Classification of Deferred Taxes [Member] | ASU Early Adoption [Member]
Summary Of Significant Accounting Policies [Line Items]
Decrease in deferred tax liability current										(600,000)
Increase in deferred tax liability non-current										600,000
Operating Lease One [Member]
Summary Of Significant Accounting Policies [Line Items]
Restricted cash deposit									$ 39,000	$ 39,000
Operating Lease Two [Member] | Multi Tenant Building [Member]
Summary Of Significant Accounting Policies [Line Items]
Restricted cash deposit									$ 500,000
Additional Office space rented under operating lease | ft²						19,805			22,067
Lease expire date						Feb. 28, 2022			Feb. 28, 2022