Stockholders Equity - Additional Information (Detail) $ / shares in Units, $ in Thousands			3 Months Ended	12 Months Ended
	Sep. 29, 2017 $ / shares shares	Jun. 14, 2017 USD ($) shares	Dec. 31, 2017 USD ($) $ / shares Plan shares	Dec. 31, 2017 USD ($) $ / shares Plan shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares
Class Of Stock [Line Items]
Common stock, shares authorized			250,000,000	250,000,000	250,000,000
Common stock, par value | $ / shares			$ 0.001	$ 0.001	$ 0.001
Common stock, voting rights				one vote per share
Shares issued from exercise of stock options				404,698
Costs incurred in raising equity | $		$ 11,700		$ 10,168	$ 1,537	$ 1,013
Deferred costs | $			$ 200	$ 200	$ 1,800
Number of stock option plans | Plan			3	3
2013, 2007 and 2004 Plans | Maximum
Class Of Stock [Line Items]
Common stock options authorized grant			11,800,000	11,800,000
2017 Plans
Class Of Stock [Line Items]
Common stock reserved for future issuance			5,200,000	5,200,000
Shares issued				0
Common Stock
Class Of Stock [Line Items]
Sale of common stock, shares				6,900,000	1,133,332	13,050,924
Shares issued from the exercise of warrants and stock options					513,440
Vesting of restricted stock units and grant of shares					50,000
Cumulative increase to equity shares value | $					$ 19,900	$ 114,300
Shares issued from exercise of stock options						29,760
Repurchase of common stock, shares					1,234,592	0
Repurchase of common stock, cost | $					$ 5,900
Common Stock | Vesting of Restricted Stock Grants
Class Of Stock [Line Items]
Repurchase of common stock, shares				16,000
Convertible Bonds | Common Stock
Class Of Stock [Line Items]
Shares issued upon conversion	795,455	7,727,273
IPO
Class Of Stock [Line Items]
Sale of common stock, shares				6,900,000
Common stock share price | $ / shares			$ 11.00	$ 11.00
Shares issued from the exercise of warrants and stock options				738,764
Vesting of restricted stock units and grant of shares				821,982
Cumulative increase to equity shares value | $				$ 186,200
Costs incurred in raising equity | $				$ 11,700
IPO | 2017 Plans
Class Of Stock [Line Items]
Common stock reserved for future issuance			1,000,000	1,000,000
IPO | Other Long-term Assets
Class Of Stock [Line Items]
Deferred costs | $					$ 1,800
IPO | Common Stock
Class Of Stock [Line Items]
Common stock share price | $ / shares			$ 11.00	$ 11.00
IPO | Convertible Bonds | Common Stock
Class Of Stock [Line Items]
Common stock share price | $ / shares	$ 11
Shares issued upon conversion				8,522,728
IPO | Licensing Agreements
Class Of Stock [Line Items]
Sale of common stock, shares				568,182
$7.50 per Share | Common Stock
Class Of Stock [Line Items]
Sale of common stock, shares					1,133,332	8,845,132
Common stock share price | $ / shares					$ 7.50	$ 7.50
$9.00 per Share | Common Stock
Class Of Stock [Line Items]
Sale of common stock, shares					315,810	1,699,267
Common stock share price | $ / shares					$ 9.00	$ 9.00
$5.00 per Share | Common Stock
Class Of Stock [Line Items]
Sale of common stock, shares						2,400,000
Common stock share price | $ / shares						$ 5.00
$5.50 per Share | Common Stock
Class Of Stock [Line Items]
Sale of common stock, shares						3,399,232
Common stock share price | $ / shares						$ 5.50
$6.50 per Share | Common Stock
Class Of Stock [Line Items]
Sale of common stock, shares						307,689
Common stock share price | $ / shares						$ 6.50
IPO Secondary
Class Of Stock [Line Items]
Costs incurred in raising equity | $			$ 200