Commitments and Contingencies - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended								12 Months Ended
	Mar. 31, 2014	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014 Building sqft	Dec. 31, 2013	Dec. 31, 2012	Jul. 31, 2011 sqft	Mar. 31, 2008 sqft	Mar. 31, 2007 sqft	Mar. 31, 2001 sqft
Commitments and Contingencies [Line Items]
Lease agreement, term	8 years 1 month												11 years	2 years	5 years	10 years
Lease agreement, space										45,000			55,694	7,350	2,500	25,000
Lease agreement, expiration date													May 31, 2023
Lease agreement, letter of credit issued													$ 200,000
Lease agreement, commencement date	Aug. 01, 2014
Future minimum rental commitment, 2015		2,420,000								2,420,000
Future minimum rental commitment, 2016		2,420,000								2,420,000
Future minimum rental commitment, 2017		1,930,000								1,930,000
Future minimum rental commitment, 2018		1,439,000								1,439,000
Lease agreement, number buildings leased										4
Operating leases, rent expense										2,735,000	2,437,000	2,183,000
Operating leases, deferred rent liabilities		1,956,068				2,028,000				1,956,068	2,028,000	329,000
Research and development expenses		1,328,000	1,650,000	1,430,000	1,201,000	1,422,000	1,430,000	2,306,000	2,183,000	5,608,693	7,340,698	10,489,811
Purchase orders, supply agreements and other contractual obligations		2,835,000								2,835,000
Before Amendment
Commitments and Contingencies [Line Items]
Lease agreement, space	55,694
Security deposit	200,000				200,000
After Amendment
Commitments and Contingencies [Line Items]
Lease agreement, space	75,594
Security deposit	450,000				450,000
Future minimum rental commitment, 2015		1,371,000								1,371,000
Future minimum rental commitment, 2016		1,371,000								1,371,000
Future minimum rental commitment, 2017		1,371,000								1,371,000
Future minimum rental commitment, 2018		1,371,000								1,371,000
Expansion Space
Commitments and Contingencies [Line Items]
Lease agreement, space	19,900
Annual rent expense	361,000
Licensing Agreements
Commitments and Contingencies [Line Items]
Research and development expenses										$ 7,000	$ 302,000	$ 55,000
Lease for three buildings
Commitments and Contingencies [Line Items]
Lease agreement, space										41,000
Lease agreement, expiration date										Jun. 30, 2017
Lease for the fourth building
Commitments and Contingencies [Line Items]
Lease agreement, space										4,000
Lease agreement, expiration date										Sep. 30, 2019