Company Restructuring (Tables)

12 Months Ended

Dec. 31, 2017

Restructuring and Related Activities [Abstract]

Schedule of changes in the restructuring liability

Changes in the restructuring liability
($ in millions)	Employee costs			Exit costs			Total liability
Balance as of December 31, 2016	$	—		$	2		$	2
Expense incurred	47			42			89
Adjustments to liability	(3		)	—			(3		)
Payments applied against liability	(29		)	(14		)	(43		)
Balance as of December 31, 2017	$	15		$	30		$	45