Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Fair value of assets and liabilities measured on a recurring basis

The following table presents the financial assets and liabilities the company records at fair value on a recurring basis identified by the level of inputs used to determine fair value. See Note 1 for the definitions of these levels and for further information on our financial instruments.

	December 31, 2020						December 31, 2019
$ in millions	Level 1		Level 2		Total		Level 1		Level 2		Total
Financial Assets (Liabilities)
Marketable securities	$	377	$	1	$	378	$	364	$	1	$	365
Marketable securities valued using NAV					18						17
Total marketable securities	377		1		396		364		1		382
Derivatives	—		—		—		—		(3)		(3)