Quarterly Results (Unaudited) - Schedule of Quarterly Financial Information (Parenthetical) (Detail) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended		12 Months Ended
	Mar. 31, 2014	Feb. 28, 2014	Mar. 31, 2014		Dec. 31, 2014
Quarterly Financial Information Disclosure [Line Items]
Deemed dividend			$ 25,559	[1]	$ 25,559
Remeasurement [Member]
Quarterly Financial Information Disclosure [Line Items]
Change in fair value of warrant liability	$ 2,300
Series D convertible preferred stock [Member]
Quarterly Financial Information Disclosure [Line Items]
Change in fair value of preferred stock call option liability		$ 9,600	9,600
Series B convertible preferred stock [Member] | Remeasurement [Member]
Quarterly Financial Information Disclosure [Line Items]
Change in fair value of warrant liability			2,300
Series E convertible preferred stock [Member]
Quarterly Financial Information Disclosure [Line Items]
Deemed dividend			$ 25,600

[1] The first quarter of 2014 also includes a deemed dividend of approximately $25.6 million, which reflected a beneficial conversion feature on the underlying Series E preferred stock, in connection with the closing of the IPO on March 26, 2014.