Cash, Cash Equivalents and Restricted Cash (Tables)

3 Months Ended

Mar. 31, 2018

Cash and Cash Equivalents [Abstract]

Schedule of cash, cash equivalents and restricted cash

	March 31,
($ 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	$	477	$	458
Current restricted cash (included in other current assets)		8		6
Noncurrent restricted cash (included in other assets)		1		1
Total cash, cash equivalents and restricted cash	$	486	$	465