Shareholders' Equity - Additional Information (Detail) - USD ($)		1 Months Ended						12 Months Ended
	Jan. 01, 2017	Aug. 31, 2016	Aug. 21, 2016	Mar. 31, 2016	Jan. 31, 2016	Feb. 28, 2015	Mar. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	May 31, 2016	Mar. 31, 2009
Class of Stock [Line Items]
Issuance of stock (in shares)			3,500,000			3,400,000	3,500,000
Share price (in USD per share)		$ 11.50				$ 20.03	$ 11.50
Proceeds from issuance of common stock and pre-funded warrants, net		$ 37,300,000				$ 79,100,000	$ 37,800,000	$ 38,039,000	$ 79,076,000	$ 37,754,000
Shares of common stock to purchase by warrant (in shares)						749,250		100,602
Exercise price of warrants (in USD per share)				$ 0.01				$ 9.94				$ 12.25
Payment of stock issuance costs						$ 4,900,000	$ 2,500,000
Warrant fair value											$ 758,000
Warrant expiration date								May 18, 2023
Proceeds from warrant exercises				$ 8,000					1,400,000
Fair value adjustment of warrants										(863,000)
Issuance of common stock utilizing At-The Market Agreement, net of commissions								$ 7,000	$ 1,436,000	$ 68,000
Stock Issued During Period, Shares, Other										28,653
Pre-funded warrants
Class of Stock [Line Items]
Share price (in USD per share)						$ 20.02
Exercise price of warrants (in USD per share)						$ 0.01
At The Market (ATM) Program
Class of Stock [Line Items]
Stock offering program, commission percent					1.70%
Stock offering program, notice period for termination					10 days
Issuance of stock (in shares)								64,565
Proceeds from issuance of common stock and pre-funded warrants, net								$ 724,000
Stock offering program, aggregate offering price					$ 50,000,000
At The Market (ATM) Program | Weighted Average
Class of Stock [Line Items]
Share price (in USD per share)								$ 11.41
Equity Option | Subsequent Event | Equity Incentive Plan 2008
Class of Stock [Line Items]
Increase in authorized shares	1,785,714
Common Stock
Class of Stock [Line Items]
Issuance of stock (in shares)								3,478,260	3,444,831	3,500,000
Issuance of common stock utilizing At-The-Market Agreement (in shares)								749,250	133,240	28,653
Issuance of common stock utilizing At-The Market Agreement, net of commissions								$ 7,000	$ 1,000	$ 0
Additional Paid-in Capital
Class of Stock [Line Items]
Issuance of common stock utilizing At-The Market Agreement, net of commissions								$ 0	$ 1,435,000	$ 68,000