Fair Value Hierarchy for Cash Equivalents and Marketable Securities (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Fair Value Assets Measured on Recurring and Nonrecurring Basis Alternative [Line Items]
Assets, Fair value disclosure	$ 11,981,192	$ 2,242,076
Fair Value, Inputs, Level 1
Fair Value Assets Measured on Recurring and Nonrecurring Basis Alternative [Line Items]
Assets, Fair value disclosure	9,848,803	2,242,076
Fair Value, Inputs, Level 2
Fair Value Assets Measured on Recurring and Nonrecurring Basis Alternative [Line Items]
Assets, Fair value disclosure	2,132,389	0
Fair Value, Inputs, Level 3
Fair Value Assets Measured on Recurring and Nonrecurring Basis Alternative [Line Items]
Assets, Fair value disclosure	0	0
Money market securities
Fair Value Assets Measured on Recurring and Nonrecurring Basis Alternative [Line Items]
Assets, Fair value disclosure	98,803	2,242,076
Money market securities | Fair Value, Inputs, Level 1
Fair Value Assets Measured on Recurring and Nonrecurring Basis Alternative [Line Items]
Assets, Fair value disclosure	98,803	2,242,076
Money market securities | Fair Value, Inputs, Level 2
Fair Value Assets Measured on Recurring and Nonrecurring Basis Alternative [Line Items]
Assets, Fair value disclosure	0	0
Money market securities | Fair Value, Inputs, Level 3
Fair Value Assets Measured on Recurring and Nonrecurring Basis Alternative [Line Items]
Assets, Fair value disclosure	0	0
Certificates of Deposit
Fair Value Assets Measured on Recurring and Nonrecurring Basis Alternative [Line Items]
Assets, Fair value disclosure	9,750,000
Certificates of Deposit | Fair Value, Inputs, Level 1
Fair Value Assets Measured on Recurring and Nonrecurring Basis Alternative [Line Items]
Assets, Fair value disclosure	9,750,000
Certificates of Deposit | Fair Value, Inputs, Level 2
Fair Value Assets Measured on Recurring and Nonrecurring Basis Alternative [Line Items]
Assets, Fair value disclosure	0
Certificates of Deposit | Fair Value, Inputs, Level 3
Fair Value Assets Measured on Recurring and Nonrecurring Basis Alternative [Line Items]
Assets, Fair value disclosure	0
Commercial paper
Fair Value Assets Measured on Recurring and Nonrecurring Basis Alternative [Line Items]
Assets, Fair value disclosure	999,707
Commercial paper | Fair Value, Inputs, Level 1
Fair Value Assets Measured on Recurring and Nonrecurring Basis Alternative [Line Items]
Assets, Fair value disclosure	0
Commercial paper | Fair Value, Inputs, Level 2
Fair Value Assets Measured on Recurring and Nonrecurring Basis Alternative [Line Items]
Assets, Fair value disclosure	999,707
Commercial paper | Fair Value, Inputs, Level 3
Fair Value Assets Measured on Recurring and Nonrecurring Basis Alternative [Line Items]
Assets, Fair value disclosure	0
Corporate notes
Fair Value Assets Measured on Recurring and Nonrecurring Basis Alternative [Line Items]
Assets, Fair value disclosure	1,132,682
Corporate notes | Fair Value, Inputs, Level 1
Fair Value Assets Measured on Recurring and Nonrecurring Basis Alternative [Line Items]
Assets, Fair value disclosure	0
Corporate notes | Fair Value, Inputs, Level 2
Fair Value Assets Measured on Recurring and Nonrecurring Basis Alternative [Line Items]
Assets, Fair value disclosure	1,132,682
Corporate notes | Fair Value, Inputs, Level 3
Fair Value Assets Measured on Recurring and Nonrecurring Basis Alternative [Line Items]
Assets, Fair value disclosure	$ 0