We classify debt securities primarily as available-for-sale. We include the unrealized gains and losses arising from the revaluation of available-for-sale debt securities, net of applicable deferred income taxes, in equity (AOCI in Statement 3). We include the unrealized gains and losses arising from the revaluation of the equity securities in Other income (expense) in Statement 1. We generally determine realized gains and losses on sales of investments using the specific identification method for available-for-sale debt and equity securities and include them in Other income (expense) in Statement 1.

The cost basis and fair value of available-for-sale debt securities with unrealized gains and losses included in equity (AOCI in Statement 3) were as follows:


Available-for-sale debt securities	December 31, 2023						December 31, 2022
(Millions of dollars)	Cost Basis		Unrealized Pretax Net Gains (Losses)		Fair Value		Cost Basis		Unrealized Pretax Net Gains (Losses)		Fair Value
Government debt securities
U.S. treasury bonds	$	10	$	—	$	10	$	9	$	—	$	9
Other U.S. and non-U.S. government bonds	62		(2)		60		60		(5)		55

Corporate debt securities
Corporate bonds and other debt securities	3,031		(36)		2,995		2,561		(95)		2,466
Asset-backed securities	195		(3)		192		187		(5)		182

Mortgage-backed debt securities
U.S. governmental agency	433		(23)		410		364		(31)		333
Residential	3		(1)		2		3		(1)		2
Commercial	137		(9)		128		127		(10)		117
Total available-for-sale debt securities	$	3,871	$	(74)	$	3,797	$	3,311	$	(147)	$	3,164


Available-for-sale debt securities in an unrealized loss position:

	December 31, 2023
	Less than 12 months 1				12 months or more 1				Total
(Millions of dollars)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Government debt securities
Other U.S. and non-U.S. government bonds	$	—	$	—	$	25	$	3	$	25	$	3


Corporate debt securities
Corporate bonds	765		—		1,011		45		1,776		45
Asset-backed securities	9		—		97		3		106		3

Mortgage-backed debt securities
U.S. governmental agency	33		—		287		25		320		25
Residential	—		—		—		—		—		—
Commercial	2		—		121		9		123		9
Total	$	809	$	—	$	1,541	$	85	$	2,350	$	85


	December 31, 2022
	Less than 12 months 1				12 months or more 1				Total
(Millions of dollars)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Government debt securities
Other U.S. and non-U.S. government bonds	$	19	$	1	$	20	$	4	$	39	$	5

Corporate debt securities
Corporate bonds	1,815		46		357		50		2,172		96
Asset-backed securities	75		2		55		3		130		5

Mortgage-backed debt securities
U.S. governmental agency	229		16		98		15		327		31
Residential	2		—		1		1		3		1
Commercial	63		5		54		5		117		10
Total	$	2,203	$	70	$	585	$	78	$	2,788	$	148

1 Indicates the length of time that individual securities have been in a continuous unrealized loss position.

The unrealized losses on our investments in government debt securities, corporate debt securities, and mortgage-backed debt securities relate to changes in underlying interest rates and credit spreads since time of purchase. We do not intend to sell the investments, and it is not likely that we will be required to sell the investments before recovery of their respective amortized cost basis. In addition, we did not expect credit-related losses on these investments as of December 31, 2023.

The cost basis and fair value of available-for-sale debt securities at December 31, 2023, by contractual maturity, are shown below. Expected maturities will differ from contractual maturities because borrowers may have the right to prepay and creditors may have the right to call obligations.



	December 31, 2023
(Millions of dollars)	Cost Basis		Fair Value
Due in one year or less	$	970	$	963
Due after one year through five years	1,996		1,966
Due after five years through ten years	253		249
Due after ten years	79		79
U.S. governmental agency mortgage-backed securities	433		410
Residential mortgage-backed securities	3		2
Commercial mortgage-backed securities	137		128
Total debt securities – available-for-sale	$	3,871	$	3,797



Sales of available-for-sale debt securities:
	Years Ended December 31,
(Millions of dollars)	2023		2022		2021
Proceeds from the sale of available-for-sale securities	$	940	$	767	$	454
Gross gains from the sale of available-for-sale securities	$	—	$	—	$	4
Gross losses from the sale of available-for-sale securities	$	1	$	5	$	—

In addition, we had $1,900 million of investments in time deposits classified as held-to-maturity debt securities as of December 31, 2023. We did not have any investments classified as held-to-maturity debt securities as of December 31, 2022. All these investments mature within one year and we include them in Prepaid expenses and other current assets in Statement 3. We record held-to-maturity debt securities at amortized cost, which approximates fair value.

For the years ended December 31, 2023 and 2022, the net unrealized gains (losses) for equity securities held at December 31, 2023 and 2022 were $(12) million and $(49) million, respectively.