The following tables summarize investments accounted for as available-for-sale securities (in thousands):


	As of June 30, 2024
	Acquisition Cost		Unrealized Gain		Unrealized Loss			Estimated Fair Value
Money market funds	$	28,130	$	—	$	—		$	28,130
U.S. government obligations		139,179		—		(53	)		139,126
Corporate debt securities		8,812		—		(11	)		8,801
Total cash equivalents and investments	$	176,121	$	—	$	(64	)	$	176,057
Classified as:
Cash equivalents								$	28,130
Short-term investments									147,927
Total cash equivalents and investments								$	176,057


	As of December 31, 2023
	Acquisition Cost		Unrealized Gain		Unrealized Loss			Estimated Fair Value
Money market funds	$	21,737	$	—	$	—		$	21,737
U.S. government obligations		92,106		58		(21	)		92,143
Corporate debt securities		4,900		5		(2	)		4,903
Total cash equivalents and investments	$	118,743	$	63	$	(23	)	$	118,783
Classified as:
Cash equivalents								$	21,737
Short-term investments									97,046
Total cash equivalents and investments								$	118,783

On June 30, 2024 and December 31, 2023, the remaining contractual maturities of all the Company’s available-for-sale investments were less than 12 months. As of June 30, 2024 and December 31, 2023, the Company has not established an allowance for credit losses for any of its available-for-sale securities.

As of June 30, 2024, there were 39 available-for-sale securities, with an estimated fair value of $145.5 million in gross unrealized loss positions. As of December 31, 2023, there were 24 available-for-sale securities, with an estimated fair value of $40.3 million in gross unrealized loss positions. Based on its review of these investments, the Company believes that the unrealized losses reflect the impact of the rising interest rate environment and were not other-than-temporary in nature.