Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2012

Summary of Significant Accounting Policies [Abstract]

Calculation of basic and diluted net loss per share

	Three Months Ended June 30,						Six Months Ended June 30,
	2012			2011			2012			2011
Numerator:
Net loss	$	(5,473	)	$	(14,567	)	$	(16,645	)	$	(27,929	)
Denominator:
Weighted-average common shares outstanding		33,078			17,903			32,429			17,887
Basic and diluted net loss per share	$	(0.17	)	$	(0.81	)	$	(0.51	)	$	(1.56	)

Outstanding securities not included in diluted net loss per share

	June 30,
	2012		2011
Options to purchase common stock		4,700		4,299
Restricted stock units		702		—
Warrants outstanding		9,091		1,266
		14,493		5,565