Fair Value Measurement

3 Months Ended

Mar. 31, 2021

Fair Value Disclosures [Abstract]

Fair Value Measurement

Fair Value Measurement

The following table presents information about our assets and liabilities that are measured at fair value on a recurring basis and indicates the level of the fair value hierarchy and the valuation techniques we utilized to determine such fair value:

	As of March 31, 2021
	Level 1		Level 2		Level 3		Total
Assets:
Corporate notes and bonds	$	—	$	510,663	$	—	$	510,663
Corporate commercial paper	—		478,442		—		478,442
Obligations of U.S. government agencies	—		4,884		—		4,884
Money market funds	123,607		—		—		123,607
Total assets	$	123,607	$	993,989	$	—	$	1,117,596
Liabilities:
Development derivative liability	$	—	$	—	$	4,597	$	4,597
	As of December 31, 2020
	Level 1		Level 2		Level 3		Total
Assets:
Corporate notes and bonds	$	—	$	687,469	$	—	$	687,469
Corporate commercial paper	—		313,497		—		313,497
Obligations of U.S. government agencies	—		2,382		—		2,382
Money market funds	179,302		—		—		179,302
Total assets	179,302		$	1,003,348	$	—	$	1,182,650
Liabilities:
Development derivative liability	$	—	$	—	$	—	$	—

Level 1 —    Quoted prices in active markets for identical assets or liabilities.

Level 2 —    Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices for identical or similar assets or liabilities in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

    We use a market approach to value our Level 2 investments. The disclosed fair value related to our investments is based on market prices from a variety of industry standard data providers and generally represents quoted prices

for similar assets in active markets or has been derived from observable market data. For the three months ended March 31, 2021, there were no transfers between Level 1 and Level 2 of the fair value hierarchy.

Level 3 —    Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. For the reconciliation of the changes in the development derivative liability and the description of the significant inputs used in estimating its fair value, see Note 4.