Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies Disclosure [Abstract]

Minimum Rental Commitments Under Long-Term Non-Cancellable Operating Leases

The amounts of minimum rental commitments under long-term non-cancellable operating leases for each of the years 2018 through 2022 and thereafter are:

($ in millions)
2018	$	39
2019	35
2020	28
2021	24
2022	17
Thereafter	51
Total	$	194