Acquisition of Level 3 - Pro Forma Information (Details) - Level 3 Parent, LLC - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017
Business Acquisition [Line Items]
Operating revenues	$ 6,031	$ 18,316
Net income	$ 194	$ 459
Basic earnings per common share (in dollars per share)	$ 0.18	$ 0.43
Diluted earnings per common share (in dollars per share)	$ 0.18	$ 0.43