Segment Information Revenue From External Customers (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information
Revenue from external customers	$ 2,032	$ 2,033	$ 2,056	$ 2,051	$ 2,053	$ 2,062	$ 2,061	$ 2,053	$ 8,172	$ 8,229	$ 6,777
Core Network Service [Member]
Segment Reporting Information
Revenue from external customers									7,767	7,757	6,208
Core Network Service [Member] | North America
Segment Reporting Information
Revenue from external customers									6,362	6,207	4,520
Core Network Service [Member] | Europe
Segment Reporting Information
Revenue from external customers									744	835	904
Core Network Service [Member] | Latin America
Segment Reporting Information
Revenue from external customers									661	715	784
Wholesale Voice Services and Other [Member]
Segment Reporting Information
Revenue from external customers									405	472	569
Wholesale Voice Services and Other [Member] | North America
Segment Reporting Information
Revenue from external customers									386	447	535
Wholesale Voice Services and Other [Member] | Europe
Segment Reporting Information
Revenue from external customers									11	14	6
Wholesale Voice Services and Other [Member] | Latin America
Segment Reporting Information
Revenue from external customers									$ 8	$ 11	$ 28