Fair Value (Tables)

12 Months Ended

Dec. 31, 2014

Fair Value Measurements.

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis

Balance at December 31, 2014	Total		Quoted Prices in Active Markets for Identical Items (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)
Common stock warrant liability	$	9,418,413	$	—	$	—	$	9,418,413

Balance at December 31, 2013	Total		Quoted Prices in Active Markets for Identical Items (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)
Common stock warrant liability	$	28,829,849	$	—	$	—	$	28,829,849

Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation

Common stock warrant liability	Fair Value Measurement Using Significant Unobservable Inputs
Beginning of period—January 1, 2014	$	28,829,849
Change in fair value of common stock warrants		52,259,898
Issuance of common stock warrants		11,773,240
Exercise of common stock warrants		(83,444,574	)
Fair value of common stock warrant liability at December 31, 2014	$	9,418,413

Common stock warrant liability	Fair Value Measurement Using Significant Unobservable Inputs
Beginning of period—January 1, 2013	$	475,825
Change in fair value of common stock warrants		37,101,818
Issuance of common stock warrants		2,451,028
Exercise of common stock warrants		(11,198,822	)
Fair value of common stock warrant liability at December 31, 2013	$	28,829,849