Long-Term Debt and Credit Facilities - Additional Information (Details)						12 Months Ended
	Jan. 31, 2020 USD ($)	Jan. 24, 2020 USD ($)	Sep. 25, 2019 USD ($)	Nov. 02, 2017	Jun. 19, 2017 USD ($) lender	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2015 USD ($)	Jan. 15, 2020 USD ($)	Nov. 29, 2019 USD ($)
Long-term Debt and Credit Facilities
Long-term debt, gross						$ 35,039,000,000
Repayments of debt						3,600,000,000	$ 1,700,000,000
Gain on debt extinguishment						$ 72,000,000	(7,000,000)	$ (5,000,000)
Coverage ratio						2.00
Debt Covenant, Period Two
Long-term Debt and Credit Facilities
Leverage ratio						4.75
Medium-term Notes
Long-term Debt and Credit Facilities
Debt instrument, periodic payment						$ 164,000,000
Senior Notes
Long-term Debt and Credit Facilities
Debt instrument, periodic payment						$ 398,000,000
Qwest Corporation
Long-term Debt and Credit Facilities
Repayments of debt							1,300,000,000
EBITDA ratio						2.85
Qwest Corporation | Medium-term Notes
Long-term Debt and Credit Facilities
Long-term debt, gross						$ 100,000,000	100,000,000
Interest rate, stated percentage						2.00%
Qwest Corporation | Senior Notes
Long-term Debt and Credit Facilities
Long-term debt, gross						$ 5,956,000,000	5,956,000,000
Qwest Corporation | Senior Notes | Subsequent Event
Long-term Debt and Credit Facilities
Repurchased face amount										$ 1,100,000,000
Qwest Corporation | Senior Notes | Minimum
Long-term Debt and Credit Facilities
Interest rate, stated percentage						6.125%
Qwest Corporation | Senior Notes | Maximum
Long-term Debt and Credit Facilities
Interest rate, stated percentage						7.75%
Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Repayments of debt						$ 2,300,000,000
Level 3 Financing, Inc. | Senior Notes
Long-term Debt and Credit Facilities
Long-term debt, gross						$ 5,515,000,000	5,315,000,000
Level 3 Financing, Inc. | Senior Notes | Minimum
Long-term Debt and Credit Facilities
Interest rate, stated percentage						4.625%
Level 3 Financing, Inc. | Senior Notes | Maximum
Long-term Debt and Credit Facilities
Interest rate, stated percentage						6.125%
CenturyLink, Inc.
Long-term Debt and Credit Facilities
Repayments of debt						$ 340,000,000
CenturyLink, Inc. | Senior Notes
Long-term Debt and Credit Facilities
Long-term debt, gross						$ 8,696,000,000	8,036,000,000
Redemption price, percentage						101.00%
CenturyLink, Inc. | Senior Notes | Minimum
Long-term Debt and Credit Facilities
Interest rate, stated percentage						5.625%
CenturyLink, Inc. | Senior Notes | Maximum
Long-term Debt and Credit Facilities
Interest rate, stated percentage						7.65%
Level 3 Parent, LLC
Long-term Debt and Credit Facilities
Repayments of debt						$ 600,000,000
Level 3 Parent, LLC | Letter of Credit | Letter of Credit
Long-term Debt and Credit Facilities
Letters of credit outstanding						23,000,000	30,000,000
Level 3 Parent, LLC | Senior Notes
Long-term Debt and Credit Facilities
Long-term debt, gross						$ 0	600,000,000
Interest rate, stated percentage						5.75%
Qwest Capital Funding, Inc
Long-term Debt and Credit Facilities
Repayments of debt						$ 345,000,000	174,000,000
Qwest Capital Funding, Inc | Senior Notes
Long-term Debt and Credit Facilities
Long-term debt, gross						$ 352,000,000	697,000,000
Qwest Capital Funding, Inc | Senior Notes | Minimum
Long-term Debt and Credit Facilities
Interest rate, stated percentage						6.875%
Qwest Capital Funding, Inc | Senior Notes | Maximum
Long-term Debt and Credit Facilities
Interest rate, stated percentage						7.75%
Embarq Corporation
Long-term Debt and Credit Facilities
Maximum indebtedness, as a percent of tangible assets						15.00%
Embarq Corporation | Senior Notes
Long-term Debt and Credit Facilities
Long-term debt, gross						$ 1,450,000,000	1,485,000,000
Interest rate, stated percentage						7.995%
New Senior Secured Credit Facilities
Long-term Debt and Credit Facilities
Long-term debt, gross					$ 10,245,000,000
2017 Revolving Credit Facility | CenturyLink Escrow, LLC | Revolving Credit Facility
Long-term Debt and Credit Facilities
Maximum borrowing capacity					$ 2,168,000,000
Lenders of credit facility | lender					18
2017 Revolving Credit Facility | CenturyLink Escrow, LLC | Revolving Credit Facility | Swingline Loan
Long-term Debt and Credit Facilities
Maximum borrowing capacity					$ 100,000,000
2017 Revolving Credit Facility | CenturyLink Escrow, LLC | Revolving Credit Facility | Letter of Credit
Long-term Debt and Credit Facilities
Maximum borrowing capacity					$ 400,000,000
2017 Revolving Credit Facility | CenturyLink, Inc. | Credit facility
Long-term Debt and Credit Facilities
Long-term debt, gross						$ 250,000,000	550,000,000
Interest rate, stated percentage						4.495%
Term Loan A | CenturyLink Escrow, LLC | Medium-term Notes
Long-term Debt and Credit Facilities
Lenders of credit facility | lender					18
Aggregate principal amount of debt issuance					$ 1,707,000,000
Term Loan A | CenturyLink Escrow, LLC | Medium-term Notes | Minimum | London Interbank Offered Rate (LIBOR)
Long-term Debt and Credit Facilities
Interest rate margin					2.25%
Term Loan A | CenturyLink Escrow, LLC | Medium-term Notes | Minimum | Base Rate
Long-term Debt and Credit Facilities
Interest rate margin					1.25%
Term Loan A | CenturyLink Escrow, LLC | Medium-term Notes | Maximum | London Interbank Offered Rate (LIBOR)
Long-term Debt and Credit Facilities
Interest rate margin					3.00%
Term Loan A | CenturyLink Escrow, LLC | Medium-term Notes | Maximum | Base Rate
Long-term Debt and Credit Facilities
Interest rate margin					2.00%
Term Loan A | CenturyLink, Inc. | Medium-term Notes
Long-term Debt and Credit Facilities
Long-term debt, gross						$ 1,536,000,000	1,622,000,000
Interest rate, stated percentage						2.75%
Term Loan A-1 | CenturyLink Escrow, LLC | Medium-term Notes
Long-term Debt and Credit Facilities
Aggregate principal amount of debt issuance					$ 370,000,000
Term Loan A-1 | CenturyLink, Inc. | Medium-term Notes
Long-term Debt and Credit Facilities
Long-term debt, gross						$ 333,000,000	351,000,000
Interest rate, stated percentage						2.75%
Term Loan B | CenturyLink Escrow, LLC | Medium-term Notes
Long-term Debt and Credit Facilities
Aggregate principal amount of debt issuance					$ 6,000,000,000.0
Term Loan B | CenturyLink Escrow, LLC | Medium-term Notes | London Interbank Offered Rate (LIBOR)
Long-term Debt and Credit Facilities
Interest rate margin				2.75%
Term Loan B | CenturyLink, Inc. | Medium-term Notes
Long-term Debt and Credit Facilities
Long-term debt, gross						$ 5,880,000,000	5,940,000,000
Interest rate, stated percentage						2.75%
Term Loan | Qwest Corporation | Medium-term Notes
Long-term Debt and Credit Facilities
Long-term debt, gross						$ 100,000,000	100,000,000
Aggregate principal amount of debt issuance									$ 100,000,000
Term Loan | Qwest Corporation | Medium-term Notes | Minimum | London Interbank Offered Rate (LIBOR)
Long-term Debt and Credit Facilities
Interest rate margin									1.50%
Term Loan | Qwest Corporation | Medium-term Notes | Minimum | Base Rate
Long-term Debt and Credit Facilities
Interest rate margin									0.50%
Term Loan | Qwest Corporation | Medium-term Notes | Maximum | London Interbank Offered Rate (LIBOR)
Long-term Debt and Credit Facilities
Interest rate margin									2.50%
Term Loan | Qwest Corporation | Medium-term Notes | Maximum | Base Rate
Long-term Debt and Credit Facilities
Interest rate margin									1.50%
Tranche B 2027 Term Loan | Level 3 Financing, Inc. | Medium-term Notes
Long-term Debt and Credit Facilities
Long-term debt, gross						$ 3,111,000,000	0
Interest rate, stated percentage						1.75%
Tranche B 2027 Term Loan | Level 3 Financing, Inc. | Medium-term Notes | London Interbank Offered Rate (LIBOR)
Long-term Debt and Credit Facilities
Interest rate margin						1.00%
Tranche B 2027 Term Loan | Level 3 Financing, Inc. | Medium-term Notes | Base Rate
Long-term Debt and Credit Facilities
Interest rate, stated percentage						0.75%
Tranche B 2027 Term Loan | Level 3 Financing, Inc. | Medium-term Notes | Federal Funds Effective Swap Rate
Long-term Debt and Credit Facilities
Interest rate margin						0.50%
Tranche B 2027 Term Loan | Level 3 Financing, Inc. | Medium-term Notes | Eurodollar
Long-term Debt and Credit Facilities
Interest rate margin						1.75%
Uncommitted Revolving Letter of Credit Facility | CenturyLink, Inc. | Letter of Credit | Letter of Credit
Long-term Debt and Credit Facilities
Maximum borrowing capacity						$ 225,000,000
Letters of credit outstanding						82,000,000	97,000,000
Collateralized Debt Obligations | Level 3 Parent, LLC | Letter of Credit | Letter of Credit
Long-term Debt and Credit Facilities
Letters of credit outstanding						18,000,000	24,000,000
Senior Notes Due 2026 | Level 3 Financing, Inc. | Senior Notes
Long-term Debt and Credit Facilities
Aggregate principal amount of debt issuance			$ 1,250,000,000
Interest rate, stated percentage			5.125%
Senior Notes Due 2026 | Level 3 Financing, Inc. | Senior Notes | Subsequent Event
Long-term Debt and Credit Facilities
Repayments of debt		$ 1,250,000,000
Senior Notes Due 2027 | Senior Notes | Subsequent Event
Long-term Debt and Credit Facilities
Aggregate principal amount of debt issuance		$ 1,250,000,000
Interest rate, stated percentage		4.00%
3.400% Senior Notes Due 2027 | Level 3 Financing, Inc. | Senior Notes
Long-term Debt and Credit Facilities
Aggregate principal amount of debt issuance											$ 750,000,000
Interest rate, stated percentage											3.40%
3.875% Senior Secured Notes Due 2029 | Level 3 Financing, Inc. | Senior Notes
Long-term Debt and Credit Facilities
Aggregate principal amount of debt issuance											$ 750,000,000
Interest rate, stated percentage											3.875%
Tranche B 2024 Term Loan | Level 3 Financing, Inc. | Medium-term Notes
Long-term Debt and Credit Facilities
Long-term debt, gross						$ 0	$ 4,611,000,000
Interest rate, stated percentage						2.25%
Tranche B 2024 Term Loan | Level 3 Financing, Inc. | Senior Notes
Long-term Debt and Credit Facilities
Repurchased face amount											$ 4,611,000,000
4.625% Senior Notes Due 2027 | Level 3 Financing, Inc. | Senior Notes
Long-term Debt and Credit Facilities
Aggregate principal amount of debt issuance			$ 1,000,000,000.0								$ 3,111,000,000
Interest rate, stated percentage			4.625%
6.125% Senior Notes due 2021 | Level 3 Financing, Inc. | Senior Notes
Long-term Debt and Credit Facilities
Interest rate, stated percentage			6.125%
Repurchased face amount			$ 240,000,000
Senior Notes, 5.75% Due 2022 | Level 3 Financing, Inc. | Senior Notes
Long-term Debt and Credit Facilities
Interest rate, stated percentage			5.75%
Repurchased face amount			$ 600,000,000
5.375% Senior Notes Due 2022 | Level 3 Financing, Inc. | Senior Notes
Long-term Debt and Credit Facilities
Aggregate principal amount of debt issuance			$ 1,000,000,000
Interest rate, stated percentage			5.375%
Repayments of debt			$ 160,000,000
Amended Credit Agreement | Subsequent Event
Long-term Debt and Credit Facilities
Aggregate principal amount of debt issuance	$ 8,699,000,000
Amended Credit Agreement | Minimum | Base Rate | Subsequent Event
Long-term Debt and Credit Facilities
Interest rate margin	0.50%
Amended Credit Agreement | Minimum | Eurodollar | Subsequent Event
Long-term Debt and Credit Facilities
Interest rate margin	1.50%
Amended Credit Agreement | Maximum | Base Rate | Subsequent Event
Long-term Debt and Credit Facilities
Interest rate margin	1.25%
Amended Credit Agreement | Maximum | Eurodollar | Subsequent Event
Long-term Debt and Credit Facilities
Interest rate margin	2.25%
Amended Credit Agreement | Credit facility | Revolving Credit Facility | Subsequent Event
Long-term Debt and Credit Facilities
Maximum borrowing capacity	$ 2,200,000,000
Amended Credit Agreement, Term Loan A | Senior Notes | Subsequent Event
Long-term Debt and Credit Facilities
Aggregate principal amount of debt issuance	1,166,000,000
Amended Credit Agreement, Term Loan A-1 | Senior Notes | Subsequent Event
Long-term Debt and Credit Facilities
Aggregate principal amount of debt issuance	333,000,000
Amended Credit Agreement, Term Loan B | Senior Notes | Subsequent Event
Long-term Debt and Credit Facilities
Aggregate principal amount of debt issuance	$ 5,000,000,000.0
Amended Credit Agreement, Term Loan B | Senior Notes | Base Rate | Subsequent Event
Long-term Debt and Credit Facilities
Interest rate margin	1.25%
Amended Credit Agreement, Term Loan B | Senior Notes | Eurodollar | Subsequent Event
Long-term Debt and Credit Facilities
Interest rate margin	2.25%
6.875% Notes Due 2033 | Qwest Corporation | Senior Notes | Subsequent Event
Long-term Debt and Credit Facilities
Interest rate, stated percentage										6.875%
Repurchased face amount										$ 850,000,000
7.125% Notes Due 2043 | Qwest Corporation | Senior Notes | Subsequent Event
Long-term Debt and Credit Facilities
Interest rate, stated percentage										7.125%
Repurchased face amount										$ 250,000,000