Lease maturity (Details) $ in Millions	Mar. 31, 2019 USD ($)
Leases [Abstract]
2019 - Operating Leases	$ 238
2019 - Financing Leases	48
2020 - Operating Leases	191
2020 - Financing Leases	66
2021 - Operating Leases	147
2021 - Financing Leases	65
2022 - Operating Leases	122
2022 - Financing Leases	65
2023 - Operating Leases	97
2023 - Financing Leases	65
Thereafter - Operating Leases	507
Thereafter - Financing Leases	151
Total lease payments - Operating Leases	1,302
Total lease payments - Financing Leases	460
Imputed interest - Operating Leases	(289)
Imputed interest - Financing Leases	(309)
Total - Operating Leases	1,013
Total - Financing Leases	$ 151