Business - Additional Information (Detail) - USD ($)		1 Months Ended		3 Months Ended		6 Months Ended		12 Months Ended
	Aug. 04, 2015	Aug. 31, 2014	Apr. 30, 2013	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2012	Jul. 29, 2015	Dec. 31, 2014	Dec. 31, 2013
Nature Of Business [Line Items]
Date of formation						Jul. 02, 2004
Proceeds from equity and debt financing						$ 129,600,000
Cash received in connection with license agreements, including upfront and milestone payments received						30,100,000
Upfront and milestone payments related to license agreement					$ 302,000		$ 302,000
Net cash used in operating activities						9,495,000	7,330,000
Accumulated deficit				$ 90,574,000		90,574,000				$ 80,201,000
Unrestricted cash and cash equivalents				43,191,000	62,812,000	43,191,000	62,812,000			$ 52,663,000	$ 12,357,000
Net loss				$ 5,684,000	$ 3,645,000	$ 10,373,000	$ 7,028,000
Common stock, shares issued				22,836,919		22,836,919				22,802,039
Public offering price per share					$ 11.00		$ 11.00
Subsequent Event [Member]
Nature Of Business [Line Items]
Common stock, shares issued	4,327,956								3,763,440
Public offering price per share	$ 18.60
Net proceeds from offering of common stock	$ 75,060,000
Maximum [Member]
Nature Of Business [Line Items]
Offering of common stock, preferred stock, debt securities and warrants						$ 150,000,000
Minimum [Member]
Nature Of Business [Line Items]
Expected period to fund operations						1 year
Maruishi Pharmaceutical Co., Ltd. [Member]
Nature Of Business [Line Items]
Upfront license fee received			$ 15,000,000
Milestone payment received		$ 480,000
Upfront and milestone payments related to license agreement				$ 0	$ 302,000	$ 0	$ 302,000
Chong Kun Dang Pharmaceutical Corporation [Member]
Nature Of Business [Line Items]
Upfront and milestone payments related to license agreement								$ 1,190,000