Long-Term Debt and Credit Facilities - Additional Information (Details) - USD ($)				9 Months Ended
	Oct. 23, 2020	Jan. 31, 2020	Jan. 24, 2020	Sep. 30, 2020	Oct. 26, 2020	Aug. 12, 2020	Jun. 15, 2020	Dec. 31, 2019
Derivative [Line Items]
Repayments of debt				$ 5,200,000,000
Loss on extinguishment of debt		$ (67,000,000)
Debt outstanding				32,592,000,000				$ 34,694,000,000
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
Qwest Corporation | Senior notes
Derivative [Line Items]
Repayments of debt				1,900,000,000
Level 3 Financing, Inc. | Senior notes
Derivative [Line Items]
Repayments of debt				2,000,000,000.0
Amended Credit Agreement
Derivative [Line Items]
Face amount		$ 8,699,000,000
Amended Credit Agreement | Base Rate | Minimum
Derivative [Line Items]
Basis spread (as a percent)		1.50%
Amended Credit Agreement | Base Rate | Maximum
Derivative [Line Items]
Basis spread (as a percent)		2.25%
Amended Credit Agreement | Eurodollar | Minimum
Derivative [Line Items]
Basis spread (as a percent)		0.50%
Amended Credit Agreement | Eurodollar | Maximum
Derivative [Line Items]
Basis spread (as a percent)		1.25%
6.625% Senior Notes | Qwest Corporation | Senior notes | Subsequent Event
Derivative [Line Items]
Face amount					$ 160,000,000
Stated interest rate					6.625%
Debt outstanding					$ 0
Term loan | CenturyLink, Inc.
Derivative [Line Items]
Repayments of debt				94,000,000
Term loan | Qwest Corporation
Derivative [Line Items]
Long-term debt				100,000,000				100,000,000
Term loan | Qwest Corporation | CoBank ACB
Derivative [Line Items]
Long-term debt				100,000,000
Term loan | Term Loan B | CenturyLink, Inc.
Derivative [Line Items]
Repayments of debt			$ 1,250,000,000
Long-term debt				4,963,000,000				5,880,000,000
Senior notes
Derivative [Line Items]
Loss on extinguishment of debt		$ (67,000,000)		(82,000,000)
Senior notes | CenturyLink, Inc.
Derivative [Line Items]
Payment of aggregate principal amount at maturity				973,000,000
Long-term debt				$ 7,645,000,000				8,696,000,000
Senior notes | CenturyLink, Inc. | Minimum
Derivative [Line Items]
Stated interest rate				5.125%
Senior notes | CenturyLink, Inc. | Maximum
Derivative [Line Items]
Stated interest rate				7.65%
Senior notes | Qwest Corporation
Derivative [Line Items]
Long-term debt				$ 4,105,000,000				5,956,000,000
Senior notes | Qwest Corporation | Minimum
Derivative [Line Items]
Stated interest rate				6.125%
Senior notes | Qwest Corporation | Maximum
Derivative [Line Items]
Stated interest rate				7.75%
Senior notes | Level 3 Financing, Inc.
Derivative [Line Items]
Long-term debt				$ 5,515,000,000				5,515,000,000
Senior notes | Level 3 Financing, Inc. | Minimum
Derivative [Line Items]
Stated interest rate				3.625%
Senior notes | Level 3 Financing, Inc. | Maximum
Derivative [Line Items]
Stated interest rate				5.375%
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
Senior notes | Amended Credit Agreement, Term Loan B | Base Rate
Derivative [Line Items]
Basis spread (as a percent)		1.25%
Senior notes | Amended Credit Agreement, Term Loan B | Eurodollar
Derivative [Line Items]
Basis spread (as a percent)		2.25%
Senior notes | 3.625% Senior Notes Due 2029 | Level 3 Financing, Inc.
Derivative [Line Items]
Face amount						$ 840,000,000
Stated interest rate						3.625%
Senior notes | 4.250% Senior Secured Notes Due 2028 | Level 3 Financing, Inc.
Derivative [Line Items]
Face amount							$ 1,200,000,000
Stated interest rate							4.25%
Senior notes | 4.000% Senior Secured Notes Due 2027 | CenturyLink, Inc.
Derivative [Line Items]
Face amount			$ 1,250,000,000
Stated interest rate			4.00%	4.00%
Long-term debt				$ 1,250,000,000				$ 0
Senior notes | 4.000% Senior Secured Notes Due 2027 | Level 3 Financing, Inc.
Derivative [Line Items]
Face amount			$ 1,250,000,000
Stated interest rate			4.00%
Credit facility | Amended Credit Agreement | Revolving Credit Facility
Derivative [Line Items]
Maximum borrowing capacity		$ 2,200,000,000
Variable rate term loan | Qwest Corporation | Subsequent Event | CoBank ACB
Derivative [Line Items]
Borrowings	$ 215,000,000