
	December 31, 2023								December 31, 2022
(in millions)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
U.S. treasury securities	$	427	$	—	$	(1)	$	426	$	415	$	—	$	(5)	$	410
U.S. government agencies securities	127		—		—		127		36		—		—		35
Non-U.S. government securities	10		—		—		10		34		—		—		34
Certificates of deposit	45		—		—		45		54		—		—		54
Corporate debt securities	1,455		4		(8)		1,451		1,452		—		(26)		1,427
Residential mortgage and asset-backed securities	366		1		—		367		335		—		(3)		333
Total	$	2,430	$	5	$	(10)	$	2,426	$	2,325	$	1	$	(34)	$	2,293

The following table summarizes information related to available-for-sale debt securities that have been in a continuous unrealized loss position, classified by length of time:


	December 31, 2023
	Less Than 12 Months				12 Months or Longer				Total
(in millions)	Gross Unrealized Losses		Estimated Fair Value		Gross Unrealized Losses		Estimated Fair Value		Gross Unrealized Losses		Estimated Fair Value
U.S. treasury securities	$	—	$	161	$	(1)	$	48	$	(1)	$	209
U.S. government agencies securities	—		106		—		2		—		108
Non-U.S. government securities	—		5		—		5		—		10
Corporate debt securities	(1)		333		(7)		546		(8)		878
Residential mortgage and asset-backed securities	—		123		—		24		—		147
Total	$	(2)	$	727	$	(8)	$	624	$	(10)	$	1,351


	December 31, 2022
	Less Than 12 Months				12 Months or Longer				Total
(in millions)	Gross Unrealized Losses		Estimated Fair Value		Gross Unrealized Losses		Estimated Fair Value		Gross Unrealized Losses		Estimated Fair Value
U.S. treasury securities	$	(2)	$	174	$	(3)	$	206	$	(5)	$	379
U.S. government agencies securities	—		21		—		—		—		21
Non-U.S. government securities	—		31		—		3		—		34
Corporate debt securities	(17)		774		(8)		439		(26)		1,213
Residential mortgage and asset-backed securities	(2)		205		(1)		56		(3)		261
Total	$	(22)	$	1,204	$	(12)	$	705	$	(34)	$	1,908

No allowance for credit losses was recognized for investments with unrealized losses as of December 31, 2023, as the unrealized losses were primarily driven by broader change in interest rates with no adverse conditions identified that would prevent the issuer from making scheduled principal and interest payments. We do not currently intend to sell, and it is not more likely than not that we will be required to sell, such investments before recovery of their amortized cost bases.


	December 31,
(in millions)	2023		2022
Cash and cash equivalents	$	83	$	75
Short-term marketable debt securities	1,179		973
Long-term marketable debt securities	1,163		1,245
Total	$	2,426	$	2,293


	December 31, 2023
(in millions)	Amortized Cost		Fair Value
Within one year	$	1,267	$	1,262
After one year through five years	1,153		1,153
After five years through ten years	9		9
After ten years	2		2
Total	$	2,430	$	2,426


	December 31,
(in millions)	2023		2022
Equity securities measured at fair value:
Cash and cash equivalents	$	4,465	$	3,831
Prepaid and other current assets	1,086		473
Other long-term assets	656		943
Equity method investments and other equity investments without readily determinable fair values:
Other long-term assets	$	340	$	423
Total	$	6,547	$	5,671

For our equity method investments in Galapagos and Arcus Biosciences, Inc. (“Arcus”), we elected and applied the fair value option as we believe it best reflects the underlying economics of these investments. Our investment in Galapagos is subject to certain lock-up provisions until August 2024 and was classified in Prepaid and other current assets and Other long-term assets as of December 31, 2023 and 2022 at $686 million and $736 million, respectively. Our investment in Arcus was classified in Prepaid and other current assets as of December 31, 2023 and 2022 at $283 million and $286 million, respectively.

The following table summarizes net unrealized gains and losses on equity securities still held as of the respective balance sheet dates, included in Other income (expense), net on our Consolidated Statements of Income:

During the years ended December 31, 2022 and 2021, Gilead donated certain equity securities at fair value to the Gilead Foundation, a California nonprofit public benefit corporation (the “Foundation”). The Foundation is a related party as certain of our officers also serve as directors of the Foundation. The donation expense of $85 million and $212 million was recorded within Selling, general and administrative expenses on our Consolidated Statements of Income during the years ended December 31, 2022 and 2021, respectively.