Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Total Revenues	$ 2,052		$ 4,139
Adjustments	(80)		(149)
Total revenue from contracts with customers	1,972		3,990
Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0		0
Transferred over Time
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	1,972		3,990
IP & Data Services
Disaggregation of Revenue [Line Items]
Total Revenues	987		1,990
Adjustments	0		0
Total revenue from contracts with customers	987		1,990
Transport & Infrastructure
Disaggregation of Revenue [Line Items]
Total Revenues	673		1,348
Adjustments	(52)		(94)
Total revenue from contracts with customers	621		1,254
Voice & Collaboration
Disaggregation of Revenue [Line Items]
Total Revenues	363		744
Adjustments	0		0
Total revenue from contracts with customers	363		744
IT & Managed Services
Disaggregation of Revenue [Line Items]
Total Revenues	1		2
Adjustments	0		0
Total revenue from contracts with customers	1		2
Other
Disaggregation of Revenue [Line Items]
Total Revenues	1	$ 2	3	$ 4
Adjustments	(1)		(3)
Total revenue from contracts with customers	0		0
Affiliate Revenues
Disaggregation of Revenue [Line Items]
Total Revenues	27		52
Adjustments	(27)		(52)
Total revenue from contracts with customers	$ 0		$ 0