Commitments, Contingencies and Other Items - Operating Leases (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Leases, Operating
Proceeds from rents received	$ 522,000,000	$ 555,000,000	$ 594,000,000
Operating leases, rent expense	64,000,000	70,000,000	72,000,000
Sublease rental income received	2,000,000	$ 2,000,000	$ 4,000,000
Operating leases:
2019	54,000,000
2020	48,000,000
2021	47,000,000
2022	43,000,000
2023	38,000,000
2024 and thereafter	134,000,000
Total future minimum payments	364,000,000
Minimum sublease rentals due in the future under non-cancelable subleases	22,000,000
Purchase Obligations
Total purchase commitments	25,000,000
2019	15,000,000
2020 & 2021	10,000,000
Right-of-Way Agreements
Operating leases:
2019	19,000,000
2020	20,000,000
2021	20,000,000
2022	20,000,000
2023	19,000,000
2024 and thereafter	102,000,000
Total future minimum payments	200,000,000
Operating Leases
Operating leases:
2019	35,000,000
2020	28,000,000
2021	27,000,000
2022	23,000,000
2023	19,000,000
2024 and thereafter	32,000,000
Total future minimum payments	$ 164,000,000