Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	1 Months Ended		3 Months Ended	12 Months Ended				1 Months Ended	12 Months Ended			1 Months Ended	12 Months Ended			1 Months Ended		0 Months Ended			1 Months Ended			2 Months Ended	12 Months Ended
	Aug. 31, 2013	Apr. 30, 2012	Sep. 30, 2013	Dec. 31, 2013 Item Segment	Dec. 31, 2012	Dec. 31, 2011	Jul. 31, 2013	Jan. 31, 2010 Life Sciences Tax Incentive Program 2010 [Member] Employees	Dec. 31, 2013 Life Sciences Tax Incentive Program 2010 [Member]	Dec. 31, 2012 Life Sciences Tax Incentive Program 2010 [Member]	Dec. 31, 2011 Life Sciences Tax Incentive Program 2010 [Member]	Jan. 31, 2011 Life Sciences Tax Incentive Program 2011 [Member] Employees	Dec. 31, 2013 Life Sciences Tax Incentive Program 2011 [Member]	Dec. 31, 2012 Life Sciences Tax Incentive Program 2011 [Member]	Dec. 31, 2011 Life Sciences Tax Incentive Program 2011 [Member]	Jan. 31, 2013 Life Sciences Tax Incentive Program 2013 [Member] Employees	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]	Dec. 31, 2013 Minimum [Member]	Dec. 31, 2013 Minimum [Member] Collaboration Revenue [Member] Customer Concentration Risk [Member] Sanofi [Member]	Dec. 31, 2012 Minimum [Member] Collaboration Revenue [Member] Customer Concentration Risk [Member] Sanofi [Member]	Dec. 31, 2013 Minimum [Member] Accounts Receivable [Member] Credit Concentration Risk [Member] Sanofi [Member]	Dec. 31, 2012 Minimum [Member] Accounts Receivable [Member] Credit Concentration Risk [Member] Sanofi [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of operating segments				1
Number of geographic segments				1
Original maturities				Three months or less
Restricted cash				$ 685,000	$ 628,000
Expected average maturities period of marketable securities classified as available-for-sale																											3 months
Realized gains (losses) recognized on the sale or maturity of securities				0	0	0
Number of issues with limited investment as per investment policy				1
Concentration risk (as a percent)																												98.00%	98.00%	98.00%	99.00%
Aggregate principal amounts																		600,000	300,000	1,600,000	2,500,000	2,500,000	2,500,000	300,000	600,000	1,600,000
Aggregate principal amount																		2,500,000			2,500,000				2,500,000
Accrued interest																	100,000	100,000			100,000				100,000
Derivative liability																		0		196,000	0		196,000		0	196,000
Tax incentive awarded								1,500,000				1,300,000				500,000
State research and development tax credits monetized								1,400,000				1,200,000				400,000
Number of incremental employees pledged to be hired								50				50				20
Performance period								5 years				5 years				5 years
Amount of benefit recognized									300,000	300,000	300,000		200,000	500,000	0
Deferred financing costs netted against the equity proceeds within stockholders' equity		2,700,000		278,000	2,748,000
Aggregate deferred financing costs							600,000
Impairment charge	$ 810,000,000		$ 0	$ 810,000