Convertible Preferred Stock and Warrants - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Apr. 30, 2014
Class of Stock [Line Items]
Preferred stock to common stock, conversion ratio					1
Issuance costs	$ 0	$ 0	$ 0	$ 4,410
Amortization of deemed dividend	$ 0	$ 0	$ 0	4,744
Common stock warrants outstanding and exercisable (in shares)	250,646		250,646
Weighted-average exercise per share (usd per share)	$ 95.21		$ 95.21
Redeemable Convertible Preferred Stock (Senior) [Member]
Class of Stock [Line Items]
Preferred stock converted into common stock			All our outstanding junior and senior preferred stock was converted into common stock on a one-to-one basis.
Issuance costs				4,410
Amortization of deemed dividend				$ 4,722
Minimum [Member]
Class of Stock [Line Items]
Common stock warrants expiration period			Feb. 29, 2016
Maximum [Member]
Class of Stock [Line Items]
Common stock warrants expiration period			Sep. 30, 2019