Long-Term Debt and Credit Facilities (Details 2) $ in Millions	Nov. 02, 2017	Nov. 01, 2017 USD ($)	Jun. 19, 2017 USD ($)	May 05, 2017 USD ($)	Sep. 30, 2017 USD ($)	Aug. 01, 2017 USD ($)	Jul. 19, 2017	Jun. 15, 2017 USD ($)	May 08, 2017 USD ($)	May 04, 2017 USD ($)	Apr. 28, 2017 USD ($)	Apr. 03, 2017 USD ($)	Dec. 31, 2016 USD ($)
Qwest Corporation | Senior notes
Long-term Debt and Credit Facilities
Long-term debt, gross					$ 7,294.0								$ 7,259.0
Qwest Corporation | Senior notes | 6.75% Notes due 2057
Long-term Debt and Credit Facilities
Debt instrument, face amount				$ 85.0							$ 575.0
Stated interest rate (percent)											6.75%
Proceeds from debt, net of issuance costs				$ 638.0
Qwest Corporation | Senior notes | 7.5% Notes due 2051
Long-term Debt and Credit Facilities
Debt instrument, face amount									$ 288.0
Stated interest rate (percent)									7.50%
Debt instrument, repurchased face amount									$ 125.0
Qwest Corporation | Senior notes | 6.5% Notes due 2017
Long-term Debt and Credit Facilities
Stated interest rate (percent)										6.50%
Debt instrument, repurchased face amount										$ 500.0
Qwest Corporation | Medium-term notes
Long-term Debt and Credit Facilities
Stated interest rate (percent)					2.99%
Long-term debt, gross					$ 100.0								100.0
Qwest Capital Funding, Inc. | Senior notes
Long-term Debt and Credit Facilities
Long-term debt, gross					$ 981.0								981.0
Embarq Corporation | Senior notes
Long-term Debt and Credit Facilities
Stated interest rate (percent)					7.995%
Long-term debt, gross					$ 1,485.0								1,485.0
Embarq Corporation | Senior notes | 8.77% Notes due 2017
Long-term Debt and Credit Facilities
Stated interest rate (percent)						8.77%
Debt instrument, repurchased face amount						$ 72.0
Embarq Corporation | First mortgage bonds
Long-term Debt and Credit Facilities
Long-term debt, gross					151.0								223.0
CenturyLink, Inc. | Senior notes
Long-term Debt and Credit Facilities
Long-term debt, gross					$ 8,125.0								8,975.0
CenturyLink, Inc. | Senior notes | 5.15% Notes due 2017
Long-term Debt and Credit Facilities
Stated interest rate (percent)								5.15%
Debt instrument, repurchased face amount								$ 350.0
CenturyLink, Inc. | Senior notes | 6.00% Noted due 2017
Long-term Debt and Credit Facilities
Stated interest rate (percent)												6.00%
Debt instrument, repurchased face amount												$ 500.0
CenturyLink, Inc. | Medium-term notes
Long-term Debt and Credit Facilities
Stated interest rate (percent)					2.99%
Long-term debt, gross					$ 319.0								336.0
CenturyLink Escrow, LLC | Credit Agreement (New Senior Secured Credit Facilities)
Long-term Debt and Credit Facilities
Long-term debt, gross			$ 9,945.0
Debt covenants description			The New Senior Secured Credit Facilities contain various representations and warranties and affirmative and negative covenants. Such covenants include, among other things and subject to certain significant exceptions, restrictions on our ability to declare or pay dividends, repurchase stock, repay certain other indebtedness, create liens, incur additional indebtedness, make investments, engage in transactions with its affiliates, dispose of assets and merge or consolidate with any other person.
CenturyLink Escrow, LLC | Medium-term notes
Long-term Debt and Credit Facilities
Stated interest rate (percent)					2.75%
Long-term debt, gross					$ 6,000.0								$ 0.0
CenturyLink Escrow, LLC | Medium-term notes | Term Loan A
Long-term Debt and Credit Facilities
Debt instrument, face amount			$ 1,575.0
Credit facility lenders			17
Debt covenants description			With respect to the Term Loan A and A-1 facilities and the New Revolving Credit Facility, the Credit Agreement requires us to maintain (i) a maximum total leverage ratio of not more than 5.00 to 1.00 between the closing date of the Level 3 acquisition and the second anniversary thereof and 4.75 to 1.00 thereafter and (ii) a minimum consolidated interest coverage ratio of at least 2.00 to 1.00, with such ratios being determined and calculated in the manner described in the Credit Agreement.
CenturyLink Escrow, LLC | Medium-term notes | Term Loan B
Long-term Debt and Credit Facilities
Debt instrument, face amount			$ 6,000.0
Stated interest rate (percent)			1.375%				2.75%
CenturyLink Escrow, LLC | Medium-term notes | Term Loan A-1
Long-term Debt and Credit Facilities
Debt instrument, face amount			$ 370.0
Debt covenants description			With respect to the Term Loan A and A-1 facilities and the New Revolving Credit Facility, the Credit Agreement requires us to maintain (i) a maximum total leverage ratio of not more than 5.00 to 1.00 between the closing date of the Level 3 acquisition and the second anniversary thereof and 4.75 to 1.00 thereafter and (ii) a minimum consolidated interest coverage ratio of at least 2.00 to 1.00, with such ratios being determined and calculated in the manner described in the Credit Agreement.
CenturyLink Escrow, LLC | Revolving credit facility | New Revolving Credit Facility
Long-term Debt and Credit Facilities
Credit facility lenders			18
Line of credit facility, maximum borrowing capacity			$ 2,000.0
Debt covenants description			With respect to the Term Loan A and A-1 facilities and the New Revolving Credit Facility, the Credit Agreement requires us to maintain (i) a maximum total leverage ratio of not more than 5.00 to 1.00 between the closing date of the Level 3 acquisition and the second anniversary thereof and 4.75 to 1.00 thereafter and (ii) a minimum consolidated interest coverage ratio of at least 2.00 to 1.00, with such ratios being determined and calculated in the manner described in the Credit Agreement.
Minimum | Qwest Corporation | Senior notes
Long-term Debt and Credit Facilities
Stated interest rate (percent)					6.125%
Minimum | Qwest Capital Funding, Inc. | Senior notes
Long-term Debt and Credit Facilities
Stated interest rate (percent)					6.50%
Minimum | Embarq Corporation | First mortgage bonds
Long-term Debt and Credit Facilities
Stated interest rate (percent)					7.125%
Minimum | CenturyLink, Inc. | Senior notes
Long-term Debt and Credit Facilities
Stated interest rate (percent)					5.625%
Minimum | CenturyLink Escrow, LLC | Medium-term notes | Term Loan A
Long-term Debt and Credit Facilities
Lending commitment per lender			$ 28.6
Minimum | CenturyLink Escrow, LLC | Revolving credit facility | New Revolving Credit Facility
Long-term Debt and Credit Facilities
Lending commitment per lender			32.8
Maximum | Qwest Corporation | Senior notes
Long-term Debt and Credit Facilities
Stated interest rate (percent)					7.75%
Maximum | Qwest Capital Funding, Inc. | Senior notes
Long-term Debt and Credit Facilities
Stated interest rate (percent)					7.75%
Maximum | Embarq Corporation | First mortgage bonds
Long-term Debt and Credit Facilities
Stated interest rate (percent)					8.77%
Maximum | CenturyLink, Inc. | Senior notes
Long-term Debt and Credit Facilities
Stated interest rate (percent)					7.65%
Maximum | CenturyLink Escrow, LLC | Medium-term notes | Term Loan A
Long-term Debt and Credit Facilities
Lending commitment per lender			132.2
Maximum | CenturyLink Escrow, LLC | Revolving credit facility | New Revolving Credit Facility
Long-term Debt and Credit Facilities
Lending commitment per lender			$ 167.8
London Interbank Offered Rate (LIBOR) | Minimum | CenturyLink Escrow, LLC | Medium-term notes | Term Loan A
Long-term Debt and Credit Facilities
Applicable margin on variable rate debt			2.25%
London Interbank Offered Rate (LIBOR) | Minimum | CenturyLink Escrow, LLC | Medium-term notes | Term Loan A-1
Long-term Debt and Credit Facilities
Applicable margin on variable rate debt			2.25%
London Interbank Offered Rate (LIBOR) | Minimum | CenturyLink Escrow, LLC | Revolving credit facility | New Revolving Credit Facility
Long-term Debt and Credit Facilities
Applicable margin on variable rate debt			2.25%
London Interbank Offered Rate (LIBOR) | Maximum | CenturyLink Escrow, LLC | Medium-term notes | Term Loan A
Long-term Debt and Credit Facilities
Applicable margin on variable rate debt			3.00%
London Interbank Offered Rate (LIBOR) | Maximum | CenturyLink Escrow, LLC | Medium-term notes | Term Loan A-1
Long-term Debt and Credit Facilities
Applicable margin on variable rate debt			3.00%
London Interbank Offered Rate (LIBOR) | Maximum | CenturyLink Escrow, LLC | Revolving credit facility | New Revolving Credit Facility
Long-term Debt and Credit Facilities
Applicable margin on variable rate debt			3.00%
Base Rate | Minimum | CenturyLink Escrow, LLC | Medium-term notes | Term Loan A
Long-term Debt and Credit Facilities
Applicable margin on variable rate debt			1.25%
Base Rate | Minimum | CenturyLink Escrow, LLC | Medium-term notes | Term Loan A-1
Long-term Debt and Credit Facilities
Applicable margin on variable rate debt			1.25%
Base Rate | Minimum | CenturyLink Escrow, LLC | Revolving credit facility | New Revolving Credit Facility
Long-term Debt and Credit Facilities
Applicable margin on variable rate debt			1.25%
Base Rate | Maximum | CenturyLink Escrow, LLC | Medium-term notes | Term Loan A
Long-term Debt and Credit Facilities
Applicable margin on variable rate debt			2.00%
Base Rate | Maximum | CenturyLink Escrow, LLC | Medium-term notes | Term Loan A-1
Long-term Debt and Credit Facilities
Applicable margin on variable rate debt			2.00%
Base Rate | Maximum | CenturyLink Escrow, LLC | Revolving credit facility | New Revolving Credit Facility
Long-term Debt and Credit Facilities
Applicable margin on variable rate debt			2.00%
Swingline Loan | CenturyLink Escrow, LLC | Revolving credit facility | New Revolving Credit Facility
Long-term Debt and Credit Facilities
Line of credit facility, maximum borrowing capacity			$ 100.0
Letter of Credit | CenturyLink Escrow, LLC | Revolving credit facility | New Revolving Credit Facility
Long-term Debt and Credit Facilities
Line of credit facility, maximum borrowing capacity			$ 400.0
Scenario, Forecast | London Interbank Offered Rate (LIBOR) | CenturyLink Escrow, LLC | Medium-term notes | Term Loan B
Long-term Debt and Credit Facilities
Applicable margin on variable rate debt	2.75%
Subsequent event | CenturyLink Escrow, LLC | Credit Agreement (New Senior Secured Credit Facilities)
Long-term Debt and Credit Facilities
Financing fees		$ 239.0
Subsequent event | CenturyLink Escrow, LLC | Medium-term notes
Long-term Debt and Credit Facilities
Long-term debt, gross		7,945.0
Subsequent event | CenturyLink Escrow, LLC | Revolving credit facility | New Revolving Credit Facility
Long-term Debt and Credit Facilities
Long-term debt, gross		$ 400.0