Employee Benefits - Pension and Post-Retirement Benefits (Details)	1 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2019 USD ($) Employee	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Employee Benefits
Collective bargaining agreements term	3 years
Collective bargaining arrangement, number of participating unionized employees | Employee		7,500
Collective bargaining arrangement, number of participating active employees and retirees | Employee		7,500
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		$ 40,000,000	$ 46,000,000	$ 44,000,000
Pension Plan | CenturyLink, Inc.
Employee Benefits
Employer contributions to benefit plan		0	500,000,000
Unfunded status		1,700,000,000	1,600,000,000
Post-Retirement Benefit Plan
Employee Benefits
Defined benefit plan, service cost		11,000,000	11,000,000	$ 12,000,000
Post-Retirement Benefit Plan | CenturyLink, Inc.
Employee Benefits
Unfunded status		$ 3,000,000,000.0	3,000,000,000
Pension, Supplemental and Other Postretirement Benefit Plans | Qwest Communications International, Inc.
Employee Benefits
Pension settlement term		30 years
Repayments on affiliate obligation		$ 76,000,000	$ 87,000,000