Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2023

Asset Retirement Obligation [Abstract]

Asset retirement obligations

The results of the reviews and other changes in asset retirement obligations during 2023 and 2022, were as follows:

	2023		2022
(Dollars in millions)
Balance at beginning of year	$	524	$	469
Additional liabilities accrued	10		19
Revisions in estimated cash outflows	(3)		11
Disposition of assets	(4)		(1)
Accretion expense	29		26
Balance at end of year	$	556	$	524