Summary of Significant Accounting Policies (Details) (USD $)	Jun. 30, 2012	Dec. 31, 2011
Common stock warrant liability [Member]
Assets and liabilities measured at fair value on a recurring basis
Liabilities measured at fair value on a recurring basis	$ 387,000	$ 345,000
Embedded derivative liabilities [Member]
Assets and liabilities measured at fair value on a recurring basis
Liabilities measured at fair value on a recurring basis	477,000	845,000
Money market fund shares [Member]
Assets and liabilities measured at fair value on a recurring basis
Assets measured at fair value on a recurring basis	12,281,000	49,752,000
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Common stock warrant liability [Member]
Assets and liabilities measured at fair value on a recurring basis
Liabilities measured at fair value on a recurring basis	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Embedded derivative liabilities [Member]
Assets and liabilities measured at fair value on a recurring basis
Liabilities measured at fair value on a recurring basis	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Money market fund shares [Member]
Assets and liabilities measured at fair value on a recurring basis
Assets measured at fair value on a recurring basis	12,281,000	49,752,000
Significant Other Observable Inputs (Level 2) [Member] | Common stock warrant liability [Member]
Assets and liabilities measured at fair value on a recurring basis
Liabilities measured at fair value on a recurring basis	0	0
Significant Other Observable Inputs (Level 2) [Member] | Embedded derivative liabilities [Member]
Assets and liabilities measured at fair value on a recurring basis
Liabilities measured at fair value on a recurring basis	0	0
Significant Other Observable Inputs (Level 2) [Member] | Money market fund shares [Member]
Assets and liabilities measured at fair value on a recurring basis
Assets measured at fair value on a recurring basis	0	0
Significant Unobservable Inputs (Level 3) [Member] | Common stock warrant liability [Member]
Assets and liabilities measured at fair value on a recurring basis
Liabilities measured at fair value on a recurring basis	387,000	345,000
Significant Unobservable Inputs (Level 3) [Member] | Embedded derivative liabilities [Member]
Assets and liabilities measured at fair value on a recurring basis
Liabilities measured at fair value on a recurring basis	477,000	845,000
Significant Unobservable Inputs (Level 3) [Member] | Money market fund shares [Member]
Assets and liabilities measured at fair value on a recurring basis
Assets measured at fair value on a recurring basis	$ 0	$ 0