Products and Services Revenues - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating revenues	$ 2,130	$ 2,162
Revenue Adjustments	(78)
Revenue from contract with customer	2,052
Transferred at Point in Time
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer	11
Transferred over Time
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer	2,041
IP & Data Services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating revenues	146	151
Revenue Adjustments	0
Revenue from contract with customer	146
Transport & Infrastructure
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating revenues	759	769
Revenue Adjustments	(26)
Revenue from contract with customer	733
Voice & Collaboration
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating revenues	460	511
Revenue Adjustments	0
Revenue from contract with customer	460
IT & Managed Services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating revenues	2	1
Revenue Adjustments	0
Revenue from contract with customer	2
Regulatory Revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating revenues	52	54
Revenue Adjustments	(52)
Revenue from contract with customer	0
Affiliate services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating revenues	711	$ 676
Revenue Adjustments	0
Revenue from contract with customer	$ 711