Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended	9 Months Ended
	Nov. 18, 2016	Nov. 30, 2016	Jun. 30, 2017	Mar. 21, 2017	Sep. 30, 2016
Class Of Stock [Line Items]
Capital stock authorized for issuance			150,000,000
Common stock, shares authorized			145,000,000		145,000,000
Common stock, par value			$ 0.001		$ 0.001
Preferred stock, shares authorized			5,000,000		5,000,000
Preferred stock, par value			$ 0.001		$ 0.001
Common stock, shares outstanding			74,772,103		69,746,685
Preferred stock, shares outstanding			0		15,652
Dividend distribution, declared date			Mar. 21, 2017
Number of rights distributed for each outstanding share of common stock				1
Dividend distribution, record date			Mar. 22, 2017
Rights expiration date			Mar. 21, 2018
ARO-LPA Agreement | Amgen
Class Of Stock [Line Items]
Common stock shares sold	1,745,810
Common stock shares sold, price per share	$ 7.16
Net proceeds received		$ 12.5
Series C Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares converted			15,652
Common stock, issued upon conversion of preferred stock			2,670,990
Preferred stock, shares outstanding			0
Series D Junior Participating Preferred
Class Of Stock [Line Items]
Preferred stock, par value				$ 0.001
Preferred stock conversion of purchase price per one one thousandth of share				$ 0.020
Beneficial ownership percentage of common stock upon right exercisable				15.00%
Number of rights distributed for each outstanding share of common stock			1
2004 Equity Incentive Plan, 2013 Equity Incentive Plan, and Inducement Grants
Class Of Stock [Line Items]
Common Stock, Share reserve for issuance			8,978,823