Employee Benefits - Pension and Post-Retirement Benefits (Details) $ in Millions	1 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2018 USD ($) Employee	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Employee Benefits
Collective bargaining agreements term	3 years
Collective bargaining arrangement, number of participating unionized employees | Employee		8,400
Collective bargaining arrangement, number of participating active employees and retirees | Employee		8,400
CenturyLink, Inc.
Employee Benefits
Allocated expenses by parent entities (as a percent)		70.00%	70.00%	70.00%
Pension Plan
Employee Benefits
Defined benefit plan, service cost		$ 46	$ 44	$ 45
Pension Plan | CenturyLink, Inc.
Employee Benefits
Employer contributions to benefit plan		500	100
Unfunded status		1,600	2,000
Post-Retirement Benefit Plan
Employee Benefits
Defined benefit plan, service cost		11	12	$ 14
Post-Retirement Benefit Plan | CenturyLink, Inc.
Employee Benefits
Unfunded status		$ 3,000	3,400
Pension, Supplemental and Other Postretirement Benefit Plans | Qwest Communications International, Inc.
Employee Benefits
Pension settlement term		30 years
Repayments on affiliate obligation		$ 87	$ 87