Related Party Transactions - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified		0 Months Ended			1 Months Ended			2 Months Ended	12 Months Ended		1 Months Ended
	Dec. 31, 2013 Silver Creek [Member]	Dec. 31, 2013 Silver Creek Convertible Note [Member] Silver Creek [Member]	Feb. 28, 2013 Silver Creek Convertible Note [Member] Silver Creek [Member]	Dec. 31, 2012 Silver Creek Convertible Note [Member] Silver Creek [Member]	Dec. 31, 2013 Silver Creek Convertible Note [Member] Silver Creek [Member]	Feb. 28, 2013 Silver Creek Convertible Note [Member] Silver Creek [Member]	Dec. 31, 2012 Silver Creek Convertible Note [Member] Silver Creek [Member]	Feb. 28, 2013 Silver Creek Convertible Note [Member] Silver Creek [Member]	Dec. 31, 2013 Silver Creek Convertible Note [Member] Silver Creek [Member]	Dec. 31, 2012 Silver Creek Convertible Note [Member] Silver Creek [Member]	Apr. 30, 2012 Sanofi [Member]	Dec. 31, 2013 Directors, Officers, Scientific Advisory Board Members and Related Parties [Member] Silver Creek Convertible Note [Member]	Feb. 28, 2013 Directors, Officers, Scientific Advisory Board Members and Related Parties [Member] Silver Creek Convertible Note [Member]	Dec. 31, 2012 Directors, Officers, Scientific Advisory Board Members and Related Parties [Member] Silver Creek Convertible Note [Member]
Related Party Transaction [Line Items]
Shares of common stock purchased by related party in connection with initial public offering											5,217,391
Debt issued		$ 0.6	$ 0.3	$ 1.6	$ 2.5	$ 2.5	$ 2.5	$ 0.3	$ 0.6	$ 1.6		$ 0.3	$ 0.3	$ 0.3
Notes and related accrued interest converted into shares of preferred stock	$ 0.1	$ 0.1			$ 0.1				$ 0.1