Revenue Recognition - Disaggregation of Revenue (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Disaggregation of Revenue [Line Items]
Total Revenues	$ 2,087
Adjustments	(44)
Total revenue from contracts with customers	2,043
Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0
Transferred over Time
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	2,043
Voice & Collaboration
Disaggregation of Revenue [Line Items]
Total Revenues	381
Adjustments	0
Total revenue from contracts with customers	381
IT & Managed Services
Disaggregation of Revenue [Line Items]
Total Revenues	1
Adjustments	0
Total revenue from contracts with customers	1
Transport & Infrastructure
Disaggregation of Revenue [Line Items]
Total Revenues	675
Adjustments	(42)
Total revenue from contracts with customers	633
IP & Data Services
Disaggregation of Revenue [Line Items]
Total Revenues	1,003
Adjustments	0
Total revenue from contracts with customers	1,003
Regulatory Revenue
Disaggregation of Revenue [Line Items]
Total Revenues	2
Adjustments	(2)
Total revenue from contracts with customers	0
Affiliate Revenues
Disaggregation of Revenue [Line Items]
Total Revenues	25
Adjustments	0
Total revenue from contracts with customers	$ 25