Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2012

Summary of Significant Accounting Policies [Abstract]

Weighted average estimates used in the Black-Scholes option-pricing model

	Three Months Ended June 30,						Six Months Ended June 30,
	2012			2011			2012			2011
Risk free interest rates		1.0	%		1.7	%		1.3	%		2.2	%
Expected life in years		5.8 years			5.5 years			5.9 years			6.3 years
Expected dividend yield		0.0	%		0.0	%		0.0	%		0.0	%
Expected volatility		71.6	%		73.2	%		70.7	%		73.9	%

Summary of stock based compensation expense included in statements of operations

	Three Months Ended June 30,				Six Months Ended June 30,
	2012		2011		2012		2011
Cost of product sales	$	78	$	76	$	187	$	132
Research and development		350		613		886		1,221
Selling, general and administrative		1,453		1,607		3,679		3,217
Total stock-based compensation expense included in loss from operations	$	1,881	$	2,296	$	4,752	$	4,570

Details of financial instruments carried at fair value

Description	Balance at June  30, 2012		Fair Value Measurements as of June 30, 2012
			Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	85,685	$	85,685	$	—	$	—
Investments in marketable securities – short-term:
Debt instruments – Municipal debt obligations		2,772		—		2,772		—
Certificates of deposit		1,000		—		1,000		—
Assets at fair value	$	89,457	$	85,685	$	3,772	$	—
Description	Balance at December 31, 2011		Fair Value Measurements as of December 31, 2011
			Level 1		Level 2		Level 3
Assets:
Cash equivalents:
Money market funds	$	74,389	$	74,389	$	—	$	—
Debt instruments – Corporate debt obligations		6,346		—		6,346		—
Investments in marketable securities – short-term:
Debt instruments – Corporate debt obligations		37,394		—		37,394		—
Debt instruments – Municipal debt obligations		6,224		—		6,224		—
Certificates of deposit		1,000		—		1,000		—
Assets at fair value	$	125,353	$	74,389	$	50,964	$	—