Stock Options - Additional Information (Detail) (USD $)	6 Months Ended		6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 Restricted Stock [Member]	Jun. 30, 2012 Restricted Stock [Member]	Jun. 30, 2013 2007 Plan [Member]	Jun. 30, 2013 2010 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options available to purchase/Common Stock outstanding	9,390,900	8,648,268			3,146,113	6,244,787
Shares authorized for issuance						11,000,000
Shares available for future grants					0	4,739,588
Exercisable period	7 years 3 months 22 days				10 years	10 years
Stock-based compensation expense, net of estimated forfeitures			$ 1,627,191	$ 767,955
Expected term of options granted			10 years
Weighted Average Exercise Price, Vested	6 years 1 month 17 days		48 months
Weighted average grant-date fair value of options granted	$ 2.71
Total fair value of options that vested	1,101,169
Total unrecognized compensation expense, related to non-vested share-based compensation arrangements	$ 6,893,312
Period for unrecognized compensation expense is estimated to be recognized	3 years