Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2024

Fair Value Disclosures [Abstract]

Schedule of Fair Value of Investment Assets

The Company's investment assets are carried at fair value on the consolidated balance sheets, within the line items Short-term Investments and Other Long-term Assets, as summarized in the following table.

	December 2024						December 2023
(Dollars in Millions)	Level 1		Level 2		Total		Level 1		Level 2		Total
Exchange-traded Funds	$	2	$	—	$	2	$	—	$	—	$	—
Fixed Income Mutual Finds	—		—		—		80		—		80
Corporate Bonds	—		71		71		—		60		60
Time Deposits	—		66		66		—		—		—
Government Securities	—		42		42		—		40		40
Asset-backed Securities	—		35		35		—		1		1
Total Investments at Fair Value	$	2	$	214	$	216	$	80	$	101	$	181
Total Investments at Amortized Cost (a)					$	218					$	184

(a) Exchange-traded funds are excluded as they are not disclosed at amortized cost.

Schedule of Investment Maturities

These investments have the following maturities and are represented on the consolidated balance sheet within short-term investments for investments with maturities of less than one year, and other long-term assets for investments with maturities of one year and greater.

(Dollars in Millions)	December 2024		December 2023
Less than 1 year	$	72	$	83
1 - 5 years	72		37
5 - 10 years	23		17
Greater than 10 years	47		44
Total Investments at Fair Value (a)	$	214	$	181

(a) Exchange-traded funds are excluded as there is no stated contractual maturity date.

Schedule of Fair Value and Carrying Value of Long-term Debt

The fair value and carrying value of the Company's long-term debt is as follows:

(Dollars in Millions)	December 2024		December 2023
Long-term Debt (Including Current Maturities):
Fair Value	$	16,481	$	17,528
Carrying Value	18,503		18,533

Schedule of Pension Plan Assets at Fair Value by Level

The pension plan assets at fair value by level, within the fair value hierarchy, as of calendar plan years 2024 and 2023 are shown in the table below. For additional information related to pension assets, see Note 9, Employee Benefit Plans.

	December 2024						December 31, 2023 (a)
(Dollars in Millions)	Level 1		Level 2		Total		Level 1		Level 2		Total
Common Stock	$	171	$	—	$	171	$	340	$	—	$	340
Mutual Funds	32		—		32		32		—		32
Cash and Cash Equivalents	514		—		514		250		—		250
Corporate Bonds	—		680		680		—		646		646
Government Securities	—		260		260		—		126		126
Asset-backed Securities, Derivatives and Other	—		14		14		—		10		10
Total Investments in the Fair Value Hierarchy	$	717	$	954	$	1,671	$	622	$	782	$	1,404
Investments Measured at Net Asset Value (b)	n/a		n/a		$	738	n/a		n/a		$	1,061
Investments at Fair Value	$	717	$	954	$	2,409	$	622	$	782	$	2,465

(a) See Note 20, Revision of Prior Period Financial Statements.

(b) Investments measured at net asset value represent certain investments that have been measured at net asset value per share (or its equivalent) and thus are not classified in the fair value hierarchy. In accordance with ASC 820, Fair Value Measurements, the fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the pension assets disclosed in Note 9, Employee Benefit Plans.