The following tables show the Company’s cash and cash equivalents and short-term investments by significant investment category as of September 30, 2020, and December 31, 2019 (in thousands):

	September 30, 2020
	Amortized cost		Gross unrealized gains		Gross unrealized losses		Estimated fair value		Cash and cash equivalents		Short-term investments
Cash	$	2,577	$	—	$	—	$	2,577	$	2,577	$	—

Level 1:
Money market funds		33,218		—		—		33,218		33,218		—
U.S. treasury securities		—		—		—		—		—		—
Subtotal		33,218		—		—		33,218		33,218		—
Level 2:
Commercial paper		—		—		—		—		—		—
Corporate debt obligations		1,432		1		—		1,433		—		1,433
Repurchase agreements		—		—		—		—		—		—
Asset-backed securities		751		—		—		751		—		751
Subtotal		2,183		1		—		2,184		—		2,184

Total	$	37,978	$	1	$	-	$	37,979	$	35,795	$	2,184

	December 31, 2019
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Estimated fair value		Cash and cash equivalents		Short-term investments
Cash	$	3,950	$	—	$	—		$	3,950	$	3,950	$	—

Level 1:
Money market funds		5,500		—		—			5,500		5,500		—
U.S. treasury securities		3,078		2		(1	)		3,079		—		3,079
Subtotal		8,578		2		(1	)		8,579		5,500		3,079
Level 2:
Commercial paper		8,920		—		—			8,920		747		8,173
Corporate debt obligations		5,922		5		(1	)		5,926		—		5,926
Repurchase agreements		3,000		—		—			3,000		3,000		—
Asset-backed securities		4,505		3		—			4,508		—		4,508
Subtotal		22,347		8		(1	)		22,354		3,747		18,607

Total	$	34,875	$	10	$	(2	)	$	34,883	$	13,197	$	21,686

The Company’s investments were primarily valued based upon one or more valuations reported by its investment accounting and reporting service provider. The investment service provider values the securities using a hierarchical security pricing model that relies primarily on valuations provided by a third-party pricing vendor. Such valuations may be based on trade prices in active markets for identical assets or liabilities (Level 1 inputs) or valuation models using inputs that are observable either directly or indirectly (Level 2 inputs), such as quoted prices for similar assets or liabilities, yield curve, volatility factors, credit spreads, default rates, loss severity, current market and contractual prices for underlying instruments or debt, broker and dealer quotes, as well as other relevant economic measures. The Company performs certain procedures to corroborate the fair value of its holdings, including comparing valuations obtained from its investment service provider with other pricing sources to validate the reasonableness of the valuations.

The Company typically invests in highly rated securities, and its investment policy limits the amount of credit exposure to any one issuer. The policy requires investments in fixed income instruments denominated and payable in U.S. dollars only and requires investments to be investment grade, with a primary objective of minimizing the potential risk of principal loss.

The Company considers the declines in market value of its short-term investments to be temporary in nature. Fair values were determined for each individual security in the investment portfolio. When evaluating an investment for other-than-temporary impairment, the Company reviews factors such as length of time and extent to which fair value has been below its cost basis, the financial condition of the issuer and any changes thereto, changes in market interest rates and the Company’s intent to sell, or whether it is more likely than not it will be required to sell the investment before recovery of the investment’s cost basis. As of September 30, 2020, and December 31, 2019, the Company does not consider any of its investments to be other-than temporarily impaired.