Cash, Cash Equivalents and Restricted Cash (Tables)

9 Months Ended

Sep. 30, 2018

Cash and Cash Equivalents [Abstract]

Schedule of cash, cash equivalents and restricted cash

	September 30,
($ in millions)	2018		2017
Beginning of period:
Cash and cash equivalents	$	448	$	597
Current restricted cash (included in other current assets)		10		9
Noncurrent restricted cash (included in other assets)		1		1
Total cash, cash equivalents and restricted cash	$	459	$	607
End of period:
Cash and cash equivalents	$	598	$	556
Current restricted cash (included in other current assets)		13		6
Noncurrent restricted cash (included in other assets)		—		1
Total cash, cash equivalents and restricted cash	$	611	$	563