Liquidity and Going Concern - Additional Information (Detail) - USD ($)					1 Months Ended		12 Months Ended
	Dec. 31, 2016	Jun. 08, 2016	May 02, 2016	Apr. 03, 2016	Oct. 31, 2014	Sep. 30, 2013	Dec. 31, 2016
Liquidity And Going Concern [Line Items]
Long-term debt	$ 47,107,000						$ 47,107,000
Maximum amount of equity and other securities authorized to offer	250,000,000						250,000,000
Remaining amount of equity and other securities authorized to offer	$ 50,000,000						50,000,000
Common stock issued and sold under sales agreement							3,600,000
Warrant exercisable period					7 years	7 years
Private Placement [Member] | Yuhan Corporation [Member]
Liquidity And Going Concern [Line Items]
Common stock agreed to issue and sell			1,801,802
Warrants to purchase common stock			235,294
Warrant exercise price per share			$ 8.50
Warrant exercisable period			3 years
Gross proceeds of common stock and warrants			$ 10,000,000
Common stock price per share			$ 5.55
ABG Purchase Agreement [Member] | Private Placement [Member]
Liquidity And Going Concern [Line Items]
Aggregate purchase price of common stock warrants & warrants				$ 50,000,000
Common stock agreed to issue and sell				9,009,005
Warrants to purchase common stock				2,702,700
Warrant exercise price per share				$ 8.50
Warrant exercisable period				3 years
ABG Purchase Agreement [Member] | Private Placement [Member] | Maximum [Member]
Liquidity And Going Concern [Line Items]
Issuance of securities for resale, period				30 days
Additional Purchase Agreements [Member] | Private Placement [Member] | Beijing Shijilongxin Investment Co Ltd [Member]
Liquidity And Going Concern [Line Items]
Aggregate purchase price of common stock warrants & warrants				$ 45,000,000
Common stock agreed to issue and sell				8,108,108
Warrants to purchase common stock				1,176,471
Warrant exercise price per share				$ 8.50
Warrant exercisable period				3 years
Additional Purchase Agreements [Member] | Private Placement [Member] | FREJOY Investment Management Co Ltd [Member]
Liquidity And Going Concern [Line Items]
Aggregate purchase price of common stock warrants & warrants				$ 45,000,000
Common stock agreed to issue and sell				8,108,108
Warrants to purchase common stock				1,176,471
Warrant exercise price per share				$ 8.50
Warrant exercisable period				3 years
Additional Purchase Agreements [Member] | Private Placement [Member] | Yuhan Corporation [Member]
Liquidity And Going Concern [Line Items]
Aggregate purchase price of common stock warrants & warrants				$ 10,000,000
Common stock agreed to issue and sell				1,801,802
Warrants to purchase common stock				235,294
Warrant exercise price per share				$ 8.50
Warrant exercisable period				3 years
ABG Purchasers, Beijing Shijilongxin, and Frejoy [Member]
Liquidity And Going Concern [Line Items]
Common stock agreed to issue and sell		25,225,221
Warrants to purchase common stock		5,055,642
Gross proceeds of common stock and warrants		$ 86,500,000
Common stock price per share		$ 5.55
Closed consideration of common stock and warrants		$ 150,000,000
Aggregate principal amount		$ 53,500,000
Cancellation and Forfeiture Agreements [Member] | Investors [Member]
Liquidity And Going Concern [Line Items]
Common stock agreed to issue and sell	7,838,259
Common stock shares forfeited	1,137,316
Cancellation and Forfeiture Agreements [Member] | Investors [Member] | Secured Promissory Notes [Member]
Liquidity And Going Concern [Line Items]
Outstanding balance of promissory note forfeited	$ 43,500,000
November 2014 Registration [Member]
Liquidity And Going Concern [Line Items]
Remaining amount of equity and other securities authorized to offer	46,400,000						46,400,000
Loan and Security Agreement [Member]
Liquidity And Going Concern [Line Items]
Long-term debt	50,000,000						50,000,000
Restricted cash and cash equivalents	$ 82,400,000						$ 82,400,000