Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2013

Accounting Policies [Abstract]

Financial Assets by Major Security Type and Liability Measured at Fair Value on Recurring Basis

The following table represents the fair value hierarchy for our financial assets (cash equivalents and marketable securities) by major security type and contingent consideration liability measured at fair value on a recurring basis as of December 31, 2013 and 2012 (in thousands):

December 31, 2013	Level 1		Level 2		Level 3		Total
Assets
Money market funds	$	11,345	$	—	$	—	$	11,345
Corporate debt securities		—		12,003		—		12,003
Total assets	$	11,345	$	12,003	$	—	$	23,348
Liabilities
Contingent consideration liability	$	—	$	—	$	39,200	$	39,200
Total liabilities	$	—	$	—	$	39,200	$	39,200

December 31, 2012	Level 1		Level 2		Level 3		Total
Assets
Money market funds	$	17,307	$	—	$	—	$	17,307
Total assets	$	17,307	$	—	$	—	$	17,307
Liabilities
Contingent consideration liability	$	—	$	—	$	9,600	$	9,600
Total liabilities	$	—	$	—	$	9,600	$	9,600

Fair Value Measurement of Contingent Consideration Liability

The following table represents a reconciliation of the change in the fair value measurement of the contingent consideration liability for the years ended December 31, 2013 and 2012 (in thousands).

	December 31,
	2013			2012
Beginning balance	$	9,600		$	16,500
Payments made		(10,313	)		(5,000	)
Adjustments to fair value measurement		39,913			(1,900	)
Ending balance	$	39,200		$	9,600

Schedule of Inventory

Inventory, which is stated at the lower of cost or estimated market value, consists of the following at December 31, 2013 (in thousands):

Raw materials	$	3,044
Work in process		—
Finished goods		403
Inventory	$	3,447

Share-based Compensation Grant Date Fair Value

During the years ended December 31, 2013, 2012 and 2011, the weighted average fair value per share of the employee stock options (excluding options issued in the Exchange Program as defined in Note 10), restricted stock units and stock purchase rights granted were:

	2013		2012		2011
Stock Options	$	3.46	$	2.60	$	10.60
Restricted Stock Units		4.67		4.96		13.30
Stock Purchase Rights		1.76		3.86		8.20

Share-based Compensation Assumptions

During the years ended December 31, 2013, 2012 and 2011, we calculated the estimated grant date fair value of stock options (excluding those issued in the Exchange Program as defined in Note 10) and stock purchase rights using the following assumptions:

	2013	2012	2011
Stock Option Plans
Weighted-average expected term	5.0 Years	5.0 Years	5.0 Years
Expected volatility	99%	98%	90%
Risk-free interest rate	0.86%	0.62%	1.52%
Dividend yield	0%	0%	0%
Employee Stock Purchase Plan
Weighted-average expected term	0.5 Years	0.6 Years	1.45 Years
Expected volatility	80%	98%	87%
Risk-free interest rate	0.70%	0.14%	0.59%
Dividend yield	0%	0%	0%

Exchange Program

The number of shares underlying the options included in the Exchange Program in 2011 and the weighted average assumptions utilized in the Black-Scholes valuation model were as follows:

	Original Options	New Options
Number of shares	212,843	80,890
Expected term	4.7 years	3.4 years
Expected volatility	94%	98%
Risk-free interest rate	1.96%	1.38%
Dividend yield	0%	0%