Receivables (Tables)

12 Months Ended

Dec. 31, 2020

Receivables [Abstract]

Schedule of accounts receivable

	As of December 31
(Dollars in millions)	2020		2019
Receivables	$	295	$	256
Allowance at beginning of year	(3)		(2)
Current period provision for expected credit losses	(1)		—
Reversal of allowance	—		1
Addition to allowance	—		(2)
Write-off against allowance	1		—
Allowance at end of year	(3)		(3)
Total receivables, net of allowance	$	292	$	253