Leases - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	9 Months Ended
	May 31, 2012 sqft	Sep. 30, 2012 Phase sqft
Future Minimum Payments Under Non-Cancelable Operating Leases With Initial Terms Of One-Year Or More [Line Items]
Area of office and laboratory in square foot		100,000
Additional square feet of office space	26,000
Operating lease term	3 years
Extended lease expiration date		2019-07
Number of consecutive renewal options		2
Operating lease renewal options, lease term in years		5 years
Future minimum annual rental payments under operating lease due 2012		$ 1.6
Future minimum annual rental payments under operating lease due 2013		6.5
Future minimum annual rental payments under operating lease due 2014		6.7
Future minimum annual rental payments under operating lease due 2015		6.2
Future minimum annual rental payments under operating lease due 2016		5.5
Future minimum annual rental payments under operating lease due 2017		5.6
Future minimum annual rental payments under operating lease due after 2017		$ 9.0