Stockholders Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended		12 Months Ended
	Oct. 20, 2016	Oct. 19, 2016	Oct. 31, 2016	Oct. 31, 2011	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Oct. 04, 2011
Stockholders Equity Note [Line Items]
Common stock, par value					$ 0.0001	$ 0.0001
Issuance of common stock, per share						$ 40.00	$ 190.00
Underwriters option exercisable period		30 days
Net proceeds from issuance of common stock						$ 161,854	$ 205,133
Issuance of common stock on exercise of option					557,080	43,751	757,038
Common stock issued upon vesting of restricted stock units					211,761
Common stock, shares authorized					100,000,000	100,000,000
Shares of stock authorized before amendment					110,000,000
Preferred stock, shares authorized					10,000,000
Preferred stock, par value					$ 0.0001
Equity method investment ownership percentage									100.00%
Common stock, shares outstanding					37,594,851	36,826,010
Warrant expiration date					Oct. 04, 2021
Issuance of common stock on exercise of option					6,134,513	6,578,522	5,542,285	3,978,126
Share based compensation awarded					519,791	1,658,465	2,606,183
Weighted-average grant date fair value of options granted					$ 24.30	$ 25.69	$ 68.30
Non Vested Stock Options
Stockholders Equity Note [Line Items]
Estimated unrecognized employee compensation cost related to non-vested stock options granted					$ 51,300
Estimated unrecognized employee compensation cost related to non-vested stock options granted, Weighted-average period of recognition					1 year 3 months 18 days
Restricted Stock Units
Stockholders Equity Note [Line Items]
Common stock issued upon vesting of restricted stock units					211,761	2,917
Estimated unrecognized employee compensation cost related to non-vested stock options granted					$ 116,000
Estimated unrecognized employee compensation cost related to non-vested stock options granted, Weighted-average period of recognition						2 years 7 months 6 days
Weighted-average grant date fair value of restricted stock units					$ 94.93	$ 54.35
2011 Plan
Stockholders Equity Note [Line Items]
Common stock shares reserved for issuance					12,529,412
Issuance of common stock on exercise of option					7,538,925
Common stock are available for future issuance					2,643,121
2017 Employment Inducement Incentive Award Plan
Stockholders Equity Note [Line Items]
Common stock shares reserved for issuance					1,000,000
Share based compensation awarded					233,250
Alan Auerbach
Stockholders Equity Note [Line Items]
Percentage of shares held by related party				21.00%
Common Stock
Stockholders Equity Note [Line Items]
Issuance of common stock (in shares)						4,312,500	1,150,000
Issuance of common stock on exercise of option					557,080	46,668	757,038
Common stock, shares outstanding					37,594,851	36,826,010	32,466,842	30,548,309
Shares of common stock that could be acquired by warrant					2,116,250
Common stock price					$ 16
Common Stock | Alan Auerbach
Stockholders Equity Note [Line Items]
Common stock, shares outstanding				18,666,733
Maximum | 2011 Plan
Stockholders Equity Note [Line Items]
Stock options granted, term					10 years
Maximum | 2017 Employment Inducement Incentive Award Plan
Stockholders Equity Note [Line Items]
Stock options granted, term					10 years
Minimum | Common Stock | Alan Auerbach
Stockholders Equity Note [Line Items]
Minimum ownership percentage of outstanding shares of common stock the president need to maintain after issuance of warrants				20.00%
Underwritten Public Offering
Stockholders Equity Note [Line Items]
Issuance of common stock (in shares)		3,750,000
Common stock, par value		$ 0.0001
Issuance of common stock, per share		$ 40.00
Net proceeds from issuance of common stock	$ 161,900		$ 161,900
Overallotment Option Exercise by Underwriters | Maximum
Stockholders Equity Note [Line Items]
Issuance of common stock (in shares)		562,500