Commitments, Contingencies and Other Items - Operating lease expense (Details) $ in Millions	Dec. 31, 2018 USD ($)
Right-of-Way Agreements
Right-of-Way Agreements, 2019	$ 77
Right-of-Way Agreements, 2020	51
Right-of-Way Agreements, 2021	38
Right-of-Way Agreements, 2022	37
Right-of-Way Agreements, 2023	37
Right-of-Way Agreements, Thereafter	225
Right-of-Way Agreements, Total	465
Operating Leases
Operating Leases, 2019	396
Operating Leases, 2020	259
Operating Leases, 2021	219
Operating Leases, 2022	164
Operating Leases, 2023	137
Operating Leases, Thereafter	613
Operating Leases, Total	1,788
Total
Right-of-Way Agreements and Facilities, 2019	473
Right-of-Way Agreements and Facilities, 2020	310
Right-of-Way Agreements and Facilities, 2021	257
Right-of-Way Agreements and Facilities, 2022	201
Right-of-Way Agreements and Facilities, 2023	174
Right-of-Way Agreements and Facilities, Thereafter	838
Right-of-Way Agreements and Facilities, Total	2,253
Future minimum sublease rentals	$ 29