Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2014

Fair Value Disclosures [Abstract]

Company's Financial Assets and Liability Measured at Fair Value on a Recurring Basis

The following fair value hierarchy table presents information about each major category of the Company’s financial assets and liability measured at fair value on a recurring basis as of December 31, 2014 and 2013:

	Fair value measurement using
($ in thousands)	Quoted prices in active markets  (Level 1)		Significant other observable inputs (Level 2)		Significant  unobservable inputs (Level 3)		Total
Balance at December 31, 2014
Assets:
Cash and cash equivalents	$	37,495	$	—	$	—	$	37,495
Liabilities:
Warrant liability	$	—	$	—	$	11,286	$	11,286

	Fair value measurement using
($ in thousands)	Quoted prices in active markets  (Level 1)		Significant other observable inputs (Level 2)		Significant  unobservable inputs (Level 3)		Total
Balance at December 31, 2013
Assets:
Cash and cash equivalents	$	60,033	$	—	$	—	$	60,033
Liabilities:
Warrant liability	$	—	$	—	$	15,216	$	15,216

Warrant liability

Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]

Reconciliation of Warrant Liability Measured at Fair Value on Recurring Basis

The reconciliation of warrant liability measured at fair value on a recurring basis using unobservable inputs (Level 3) is as follows:

($ in thousands)	Warrant Liability
Balance at December 31, 2011	$	23,754
Issuance of additional warrants	6,766
Exercise of warrants	(11		)
Extinguishment of debt related to warrants	4,410
Change in fair value of warrant liability	(20,404		)
Balance at December 31, 2012	$	14,515
Exercise of warrants	(352		)
Cancellation of warrants	(41		)
Change in fair value of warrant liability	1,094
Balance at December 31, 2013	$	15,216
Exercise of warrants	—
Cancellation of warrants	—
Change in fair value of warrant liability	(3,930		)
Balance at December 31, 2014	$	11,286

Derivative Liability

Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]

Reconciliation of Warrant Liability Measured at Fair Value on Recurring Basis

The reconciliation of derivative liability measured at fair value on a recurring basis using unobservable inputs (Level 3) is as follows:

	Derivative Liability
Balance at January 1, 2012	534
Issuance of additional preferred stock and other	793
Conversion of preferred stock	(1,350	)
Change in fair value of derivative liability	23
Balance at December 31, 2012	—