Investments

12 Months Ended

Dec. 31, 2020

Investments, Debt and Equity Securities [Abstract]

The following tables summarize the Company's short-term investments (in thousands):


		As of December 31, 2020
	Maturity	Amortized cost		Gross unrealized gains		Gross unrealized losses		Estimated fair value
Corporate debt securities	2 years or less	$	130,814	$	160	$	(4)	$	130,970
Commercial paper	1 year or less	240,725		58		(18)		240,765
U.S. Agency bonds	2 years or less	83,227		37		(1)		83,263
U.S. Treasury bills	2 years or less	49,539		10		(3)		49,546
		$	504,305	$	265	$	(26)	$	504,544


		As of December 31, 2019
	Maturity	Amortized cost		Gross unrealized gains		Gross unrealized losses		Estimated fair value
Corporate debt securities	2 years or less	$	160,065	$	233	$	(1)	$	160,297
Commercial paper	1 year or less	120,862		74		—		120,936
U.S. Agency bonds	2 years or less	50,745		41		(4)		50,782
U.S. Treasury bills	2 years or less	36,474		27		(1)		36,500
		$	368,146	$	375	$	(6)	$	368,515

The Company has classified all of its short-term investments as available-for-sale as the sale of such securities may be required prior to maturity to implement management strategies, and accordingly, carries these investments at fair value. As of December 31, 2020, and December 31, 2019, aggregated gross unrealized losses of available-for-sale investments were not material, and accordingly, no allowance for credit losses was recorded.

As of December 31, 2020, the Company held 588,235 shares of ORIC Pharmaceuticals, Inc. ("ORIC") common stock subject to certain transfer restrictions. The shares held by the Company are measured at fair value at each reporting period based on the closing price of ORIC's common stock on the last trading day of each reporting period, adjusted for a discount for lack of marketability, with any unrealized gains and losses recorded in the Company's consolidated statements of operations and comprehensive loss. See Note 5 for further details.