Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2020

Fair Value of Financial Assets and Liabilities Measured on Recurring Basis

The following table sets forth the fair value of our financial assets and liabilities (excluding restricted cash) allocated into Level 1 and Level 2 that were measured on a recurring basis (in thousands):



		March 31, 2020									December 31, 2019
	Fair Value Hierarchy	Amortized Cost		Unrealized Gain		Unrealized (Loss)			Estimated Fair Value		Amortized Cost		Unrealized Gain		Unrealized (Loss)			Estimated Fair Value
Money market funds	Level 1	$	54,735	$	—	$	—		$	54,735	$	23,826	$	—	$	—		$	23,826
Corporate notes and commercial paper	Level 2	207,206		64		(76		)	207,194		284,410		9		(20		)	284,399
U.S. Treasury bills and government agency securities	Level 2	84,250		608		—			84,858		96,196		48		(1		)	96,243
		$	346,191	$	672	$	(76	)	$	346,787	$	404,432	$	57	$	(21	)	$	404,468

		March 31, 2020									December 31, 2019
Classified as:		Amortized Cost		Unrealized Gain		Unrealized (Loss)			Estimated Fair Value		Amortized Cost		Unrealized Gain		Unrealized (Loss)			Estimated Fair Value
Cash equivalents		$	148,944	$	18	$	—		$	148,962	$	153,453	$	—	$	—		$	153,453
Short-term investments		166,314		407		(60		)	166,661		214,029		35		(10		)	214,054
Long-term investments		30,933		247		(16		)	31,164		36,950		22		(11		)	36,961
		$	346,191	$	672	$	(76	)	$	346,787	$	404,432	$	57	$	(21	)	$	404,468

Summary of Changes in Estimated Fair Value

The following table summarizes the changes in the estimated fair value of our embedded derivative liabilities during the three-month period ended March 31, 2020 (in thousands):



	Embedded derivative liabilities
Balance as of December 31, 2019	$	3,866
Net change in the fair value	3,169
Balance as of March 31, 2020	$	7,035

Summary of the Significant Unobservable Inputs in the Fair Value Measurement of Level 3 Liabilities

The following table summarizes the significant unobservable inputs in the fair value measurement of our Level 3 liabilities as of March 31, 2020 (in thousands):



Level 3 Liabilities	Fair value as of March 31, 2020		Valuation Technique	Unobservable Input	Range	Weighted Average
Notes payable and Long-term royalty based debt	$	151,000	Monte Carlo	Discount rate	13.99% to 14.58%	14.15%
Long-term debt	113,708		Discounted Cash Flow	Discount rate	13.46% to 13.84%	13.74%
Embedded derivative liabilities	7,035		Monte Carlo and Discounted Cash Flow	Discount rate	13.46% to 14.58%	14.04%