Long-Term Debt and Credit Facilities - Additional Information (Details) - USD ($)			3 Months Ended
	Jan. 31, 2020	Jan. 24, 2020	Mar. 31, 2020	Apr. 01, 2020
Derivative [Line Items]
Repayments of debt			$ 2,400,000,000
Gain (loss) on extinguishment of debt	$ (67,000,000)
Amended Credit Agreement
Derivative [Line Items]
Face amount	8,699,000,000
Senior notes
Derivative [Line Items]
Gain (loss) on extinguishment of debt			79,000,000
Senior notes | Senior Notes Due 2027
Derivative [Line Items]
Face amount		$ 1,250,000,000
Stated interest rate		4.00%
Senior notes | Amended Credit Agreement, Term Loan A
Derivative [Line Items]
Face amount	1,166,000,000
Senior notes | Amended Credit Agreement, Term Loan A-1
Derivative [Line Items]
Face amount	333,000,000
Senior notes | Amended Credit Agreement, Term Loan B
Derivative [Line Items]
Face amount	5,000,000,000.0
Medium-term notes
Derivative [Line Items]
Repayments of debt			31,000,000
Level 3 Financing, Inc. | Senior notes | Senior Notes Due 2026
Derivative [Line Items]
Repayments of debt		$ 1,250,000,000
CenturyLink, Inc.
Derivative [Line Items]
Repayments of debt			1,250,000,000
CenturyLink, Inc. | Senior notes
Derivative [Line Items]
Repayments of debt			$ 78,000,000
CenturyLink, Inc. | Senior notes | 4.000% Senior Secured Notes Due 2027
Derivative [Line Items]
Face amount		$ 1,250,000,000
Stated interest rate		4.00%	4.00%
CenturyLink, Inc. | Senior notes | 4.000% Senior Secured Notes Due 2027 | Subsequent Event
Derivative [Line Items]
Repurchased face amount				$ 973,000,000
Qwest Capital Funding, Inc. | Senior notes
Derivative [Line Items]
Repayments of debt			$ 1,100,000,000
Revolving Credit Facility | Credit Facility | Amended Credit Agreement
Derivative [Line Items]
Maximum borrowing capacity	$ 2,200,000,000
Base Rate | Senior notes | Amended Credit Agreement, Term Loan B
Derivative [Line Items]
Basis spread	1.25%
Eurodollar | Senior notes | Amended Credit Agreement, Term Loan B
Derivative [Line Items]
Basis spread	2.25%
Minimum | Level 3 Financing, Inc. | Senior notes
Derivative [Line Items]
Stated interest rate			4.625%
Minimum | CenturyLink, Inc. | Senior notes
Derivative [Line Items]
Stated interest rate			5.125%
Minimum | Qwest Capital Funding, Inc. | Senior notes
Derivative [Line Items]
Stated interest rate			6.875%
Minimum | Base Rate | Amended Credit Agreement
Derivative [Line Items]
Basis spread	1.50%
Minimum | Eurodollar | Amended Credit Agreement
Derivative [Line Items]
Basis spread	0.50%
Maximum | Level 3 Financing, Inc. | Senior notes
Derivative [Line Items]
Stated interest rate			5.625%
Maximum | CenturyLink, Inc. | Senior notes
Derivative [Line Items]
Stated interest rate			7.65%
Maximum | Qwest Capital Funding, Inc. | Senior notes
Derivative [Line Items]
Stated interest rate			7.75%
Maximum | Base Rate | Amended Credit Agreement
Derivative [Line Items]
Basis spread	2.25%
Maximum | Eurodollar | Amended Credit Agreement
Derivative [Line Items]
Basis spread	1.25%