Employee Benefits (Details 3) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Contribution Plan [Abstract]
CenturyLink, Inc. common stock included in the assets of the Defined Contribution Plan (in shares)	7	7
Expenses related to the 401(k) Plan	$ 77	$ 79	$ 83