Commitments, Contingencies and Other Items - Other Commitments (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) year	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Amount outstanding under letters of credit	$ 46	$ 28
Collateralized Financings	43	23
Payments under these right-of-way agreements	211	173	$ 161
Rent expense, including common area maintenance, under non-cancelable lease agreements	357	$ 318	$ 311
Right-of-Way Agreements
Right-of-Way Agreements, 2013	151
Right-of-Way Agreements, 2014	72
Right-of-Way Agreements, 2015	69
Right-of-Way Agreements, 2016	59
Right-of-Way Agreements, 2017	54
Right-of-Way Agreements, Thereafter	295
Right-of-Way Agreements, Total	700
Facilities
Facilities, 2013	278
Facilities, 2014	245
Facilities, 2015	209
Facilities, 2016	157
Facilities, 2017	123
Facilities, Thereafter	578
Facilities, Total	1,590
Total
Right-of-Way Agreements and Facilities, 2013	429
Right-of-Way Agreements and Facilities, 2014	317
Right-of-Way Agreements and Facilities, 2015	278
Right-of-Way Agreements and Facilities, 2016	216
Right-of-Way Agreements and Facilities, 2017	177
Right-of-Way Agreements and Facilities, Thereafter	873
Right-of-Way Agreements and Facilities, Total	2,290
Future Minimum Sublease Receipts
2013	4
2014	4
2015	3
2016	2
2017	0
Thereafter	0
Total	$ 13
Period of Right-of-Way Agreements with cancelable agreements (in years) | year	1