Fair Value of Financial Instruments (Details 3) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Warrant Liability
Initial value of interest make-whole payment associated with the convertible notes	$ (13,354,000)	$ (710,000)	$ (85,000)
Reduction due to conversion of debt to equity	(42,417,000)
Carrying value of the convertible notes	34,393,000
Estimated fair value of the convertible notes	79,800,000
Common stock warrant
Warrant Liability
Balance at the beginning of the period	251,000	697,000
Exercise of warrants		(1,156,000)
Initial value of interest make-whole payment associated with the convertible notes	9,270,000
Changes in fair value of derivative liabilities and warrants included in earnings	13,354,000	710,000
Reduction due to conversion of debt to equity	(10,231,000)
Balance at the end of the period	$ 12,644,000	$ 251,000