Commitments, Contingencies and Other Items - Other Commitments (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) year	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Amount outstanding under letters of credit	$ 39	$ 46
Collateralized Financings	33	43
Payments under these right-of-way agreements	205	211	$ 173
Rent expense, including common area maintenance, under non-cancelable lease agreements	347	$ 357	$ 318
Right-of-Way Agreements
Right-of-Way Agreements, 2017	162
Right-of-Way Agreements, 2018	80
Right-of-Way Agreements, 2019	71
Right-of-Way Agreements, 2020	55
Right-of-Way Agreements, 2021	50
Right-of-Way Agreements, Thereafter	325
Right-of-Way Agreements, Total	743
Facilities
Facilities, 2017	282
Facilities, 2018	244
Facilities, 2019	222
Facilities, 2020	164
Facilities, 2021	124
Facilities, Thereafter	501
Facilities, Total	1,537
Total
Right-of-Way Agreements and Facilities, 2017	444
Right-of-Way Agreements and Facilities, 2018	324
Right-of-Way Agreements and Facilities, 2019	293
Right-of-Way Agreements and Facilities, 2020	219
Right-of-Way Agreements and Facilities, 2021	174
Right-of-Way Agreements and Facilities, Thereafter	826
Right-of-Way Agreements and Facilities, Total	2,280
Future Minimum Sublease Receipts
2017	4
2018	4
2019	3
2020	1
2021	0
Thereafter	0
Total	$ 12
Period of Right-of-Way Agreements with cancelable agreements (in years) | year	1