Subsequent Events - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended			1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 31, 2015	Jun. 12, 2014
Subsequent Event [Line Items]
Common stock, par value	$ 0.001	$ 0.001			$ 0.001
Net proceeds from public offering	$ 18,488	$ 61,425	$ 14,226
Underwriting discounts and other issuance costs	470	2,733	550
Subsequent Event
Subsequent Event [Line Items]
Common stock, shares issued				14,636,363
Common stock, par value				$ 0.001
Public offering, price per share				$ 5.50
Net proceeds from public offering				75,700
Underwriting discounts and other issuance costs				$ 5,100