Collaboration Agreement - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended			3 Months Ended		9 Months Ended		1 Months Ended	12 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Sep. 30, 2014 Collaborative Arrangement [Member]	Sep. 30, 2013 Collaborative Arrangement [Member]	Sep. 30, 2014 Collaborative Arrangement [Member]	Sep. 30, 2013 Collaborative Arrangement [Member]	Mar. 31, 2014 Upfront Payment Arrangement [Member] Collaborative Arrangement [Member]	Sep. 30, 2015 Scenario, Forecast [Member] Collaborative Arrangement [Member]	Sep. 30, 2014 Maximum [Member] Scenario, Forecast [Member] Collaborative Arrangement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration agreement upfront payment										$ 5,800,000
Amount of certain milestones achieved			40,000,000			800,000						17,000,000
Amount of certain milestones achieved in account receivable	15,266,000		15,266,000		8,331,000	5,000,000		5,000,000
Revenue recognized under collaboration agreement	1,079,000	0	1,697,000	0		1,100,000	0	1,700,000	0		2,600,000
Deferred revenue recorded under collaboration agreement						$ 9,100,000		$ 9,100,000