Other Financial Information - Other Current Assets (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Other Current Assets [Line Items]
Prepaid expenses	$ 68
Material, supplies and inventory	3
Deferred activation and installation charges	17
Other	29
Total other current assets	$ 117
Predecessor
Other Current Assets [Line Items]
Prepaid expenses		$ 82
Material, supplies and inventory		3
Deferred activation and installation charges		5
Other		25
Total other current assets		$ 115