Acquisition (Tables)

12 Months Ended

Dec. 31, 2017

Business Combinations [Abstract]

Future amortization expense

Amortization expense of intangible assets for the next five years and thereafter
($ in millions)
2018	$	82
2019	72
2020	62
2021	52
2022	42
Thereafter	84
Total amortization	$	394