Stockholders' Equity - Additional Information 1 (Detail) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2012
Class Of Stock [Line Items]
Issuances of common stock from stock option exercises, Shares			205,684	183,796
Weighted-average remaining contractual term of options exercisable			7 years 9 months 26 days
Weighted-average remaining contractual term of options outstanding			8 years 3 months 11 days
Total unrecognized compensation cost related to unvested stock option grants			$ 15,115,000
Research and development expense [Member]
Class Of Stock [Line Items]
Total employee stock-based compensation recorded as operating expenses	4,000	0	15,000	16,000	23,000
General and administrative expense [Member]
Class Of Stock [Line Items]
Total employee stock-based compensation recorded as operating expenses	474,000	0	406,000	801,000	812,000
Stock options [Member]
Class Of Stock [Line Items]
Total employee stock-based compensation recorded as operating expenses	370,000	4,000	6,599,000	3,783,000	600,000
Total unrecognized compensation cost related, weighted average period			2 years 9 months 7 days
Stock options [Member] | Research and development expense [Member]
Class Of Stock [Line Items]
Total employee stock-based compensation recorded as operating expenses	58,000		1,175,000	462,000	81,000
Stock options [Member] | General and administrative expense [Member]
Class Of Stock [Line Items]
Total employee stock-based compensation recorded as operating expenses	$ 312,000	$ 4,000	$ 5,424,000	$ 3,321,000	$ 519,000
Restricted stock units (RSUs) [Member]
Class Of Stock [Line Items]
Stock option granted with immediate vesting	24,690		137,816	218,655	89,674
2012 Plan [Member]
Class Of Stock [Line Items]
Issuances of common stock from stock option exercises, Shares			1,429,191	2,519,572
Remaining options vest			36 months
Stock option granted, restricted portion			56,500	99,500
2012 Plan [Member] | Stock options [Member]
Class Of Stock [Line Items]
Restricted stock vesting conditions			stock options generally vest on the one year anniversary of the grant date, quarterly over a three year period, or over a four-year period, with a quarter vesting on either the one year anniversary of employment or the one year anniversary of the vesting commencement date
2012 Plan [Member] | Restricted stock units (RSUs) [Member]
Class Of Stock [Line Items]
Stock option granted with immediate vesting			139,316	218,655
One Year Vesting [Member] | 2012 Plan [Member]
Class Of Stock [Line Items]
Stock option granted, restricted portion			128,500	122,500