Commitments, Contingencies and Other Items - Other Commitments (Details) - USD ($) $ in Millions	2 Months Ended	10 Months Ended	12 Months Ended
	Dec. 31, 2017	Oct. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Amount outstanding under letters of credit	$ 36		$ 36	$ 39
Collateralized Financings	30		30	33
Operating Leased Assets [Line Items]
Payments under these right-of-way agreements	35
Rent expense, including common area maintenance, under non-cancelable lease agreements	60
Right-of-Way Agreements
Right-of-Way Agreements, 2018	173		173
Right-of-Way Agreements, 2019	90		90
Right-of-Way Agreements, 2020	77		77
Right-of-Way Agreements, 2021	60		60
Right-of-Way Agreements, 2022	56		56
Right-of-Way Agreements, Thereafter	464		464
Right-of-Way Agreements, Total	920		920
Operating Leases
Operating Leases, 2018	288		288
Operating Leases, 2019	251		251
Operating Leases, 2020	217		217
Operating Leases, 2021	151		151
Operating Leases, 2022	128		128
Operating Leases, Thereafter	507		507
Operating Leases, Total	1,542		1,542
Total
Right-of-Way Agreements and Facilities, 2018	461		461
Right-of-Way Agreements and Facilities, 2019	341		341
Right-of-Way Agreements and Facilities, 2020	294		294
Right-of-Way Agreements and Facilities, 2021	211		211
Right-of-Way Agreements and Facilities, 2022	184		184
Right-of-Way Agreements and Facilities, Thereafter	971		971
Right-of-Way Agreements and Facilities, Total	2,462		2,462
Future Minimum Sublease Receipts
2018	3		3
2019	2		2
2020	1		1
2021	1		1
2022	1		1
Thereafter	1		1
Total	$ 9		$ 9
Period of Right-of-Way Agreements with cancelable agreements (in years)			1 year
Predecessor
Operating Leased Assets [Line Items]
Payments under these right-of-way agreements		$ 164		205	$ 211
Rent expense, including common area maintenance, under non-cancelable lease agreements		$ 283		$ 347	$ 357