Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2016

Fair value of assets and liabilities measured on a recurring basis

The following table presents the financial assets and liabilities we record 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.



	December 31, 2016						December 31, 2015
$ in millions	Level 1		Level 2		Total		Level 1		Level 2		Total
Financial Assets (Liabilities)
Marketable securities
Trading	$	321	$	2	$	323	$	301		$ 2	$	303
Available-for-sale	7		—		7		7		—		7
Derivatives	—		8		8		—		5		5