Long-Term Debt and Credit Facilities - Long Term Debt (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 22, 2024	Dec. 31, 2023
Long-term Debt and Credit Facilities
Finance lease and other obligations	$ 279		$ 285
Unamortized discounts, net	(492)		(4)
Unamortized debt issuance costs	(242)		(145)
Total long-term debt	18,677		19,988
Less current maturities	(86)		(157)
Long-term debt, excluding current maturities	$ 18,591		$ 19,831
Long-term debt, weighted average interest rate	7.73%		6.23%
SOFR | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Basis spread (as a percent)	6.56%
Term Loan | Qwest Corporation
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 0		$ 215
Long-term debt, weighted average interest rate			7.97%
Term Loan | SOFR | Qwest Corporation
Long-term Debt and Credit Facilities
Basis spread (as a percent)	2.50%
Series A Revolving Credit Facility | Line of Credit
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 0		$ 0
Long-term debt, weighted average interest rate	8.05%
Series A Revolving Credit Facility | Line of Credit | SOFR
Long-term Debt and Credit Facilities
Basis spread (as a percent)	4.00%
Series B Revolving Credit Facility | Line of Credit
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 0		0
Long-term debt, weighted average interest rate	10.05%
Series B Revolving Credit Facility | Line of Credit | SOFR
Long-term Debt and Credit Facilities
Basis spread (as a percent)	6.00%
Term Loan A | Term Loan
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 372		$ 0
Long-term debt, weighted average interest rate	11.329%		7.47%
Term Loan A | Term Loan | SOFR
Long-term Debt and Credit Facilities
Basis spread (as a percent)	6.00%
Term Loan B-1 | Term Loan
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 1,625		$ 0
Long-term debt, weighted average interest rate	7.739%
Term Loan B-1 | Term Loan | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 1,199		0
Long-term debt, weighted average interest rate	11.889%
Term Loan B-1 | Term Loan | SOFR
Long-term Debt and Credit Facilities
Basis spread (as a percent)	2.35%
Term Loan B-1 | Term Loan | SOFR | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Basis spread (as a percent)	6.56%
Term Loan B-2 | Term Loan
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 1,625		0
Long-term debt, weighted average interest rate	7.739%
Term Loan B-2 | Term Loan | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 1,199		0
Long-term debt, weighted average interest rate	11.889%
Term Loan B-2 | Term Loan | SOFR
Long-term Debt and Credit Facilities
Basis spread (as a percent)	2.35%
Term Loan B-2 | Term Loan | SOFR | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Basis spread (as a percent)	6.56%
Term Loan B | Term Loan
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 57		$ 3,891
Long-term debt, weighted average interest rate	7.695%		7.72%
Term Loan B | Term Loan | SOFR
Long-term Debt and Credit Facilities
Basis spread (as a percent)	2.25%
Other Facilities | Line of Credit and Term Loan
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 0		$ 1,399
Other Facilities | Line of Credit and Term Loan | SOFR
Long-term Debt and Credit Facilities
Basis spread (as a percent)	2.00%
4.125% Senior Secured Notes Due 2029-2030 | Senior Notes
Long-term Debt and Credit Facilities
Stated interest rate	4.125%
Long-term debt, gross	$ 812		0
4.000% Senior Secured Notes Due 2027 | Senior Notes
Long-term Debt and Credit Facilities
Stated interest rate	4.00%	4.00%
Long-term debt, gross	$ 0		1,250
Tranche B 2027 Term Loan | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 12		$ 2,411
Tranche B 2027 Term Loan | SOFR | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Basis spread (as a percent)	1.75%
Tranche B 2027 Term Loan | Term Loan | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 12
Long-term debt, weighted average interest rate	7.195%		7.22%
First Lien Notes | Senior Notes | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 3,846		$ 925
First Lien Notes | Senior Notes | Level 3 Financing, Inc. | Minimum
Long-term Debt and Credit Facilities
Stated interest rate	10.50%
First Lien Notes | Senior Notes | Level 3 Financing, Inc. | Maximum
Long-term Debt and Credit Facilities
Stated interest rate	11.00%
Second Lien Notes | Senior Notes | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 2,229		0
Second Lien Notes | Senior Notes | Level 3 Financing, Inc. | Minimum
Long-term Debt and Credit Facilities
Stated interest rate	3.875%
Second Lien Notes | Senior Notes | Level 3 Financing, Inc. | Maximum
Long-term Debt and Credit Facilities
Stated interest rate	4.875%
Former Level 3 Senior Notes | Senior Notes | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 0		1,500
Former Level 3 Senior Notes | Senior Notes | Level 3 Financing, Inc. | Minimum
Long-term Debt and Credit Facilities
Stated interest rate	3.40%
Former Level 3 Senior Notes | Senior Notes | Level 3 Financing, Inc. | Maximum
Long-term Debt and Credit Facilities
Stated interest rate	3.875%
Senior Notes Maturing 2025-2042 | Senior Notes
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 2,113		2,143
Senior Notes Maturing 2025-2042 | Senior Notes | Minimum
Long-term Debt and Credit Facilities
Stated interest rate	4.00%
Senior Notes Maturing 2025-2042 | Senior Notes | Maximum
Long-term Debt and Credit Facilities
Stated interest rate	7.65%
Senior Notes Maturing 2027-2029 | Senior Notes | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 1,865		3,940
Senior Notes Maturing 2027-2029 | Senior Notes | Level 3 Financing, Inc. | Minimum
Long-term Debt and Credit Facilities
Stated interest rate	3.40%
Senior Notes Maturing 2027-2029 | Senior Notes | Level 3 Financing, Inc. | Maximum
Long-term Debt and Credit Facilities
Stated interest rate	4.625%
Senior Notes Maturing 2025-2057 | Senior Notes | Qwest Corporation
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 1,986		1,986
Senior Notes Maturing 2025-2057 | Senior Notes | Qwest Corporation | Minimum
Long-term Debt and Credit Facilities
Stated interest rate	6.50%
Senior Notes Maturing 2025-2057 | Senior Notes | Qwest Corporation | Maximum
Long-term Debt and Credit Facilities
Stated interest rate	7.75%
Senior Notes Maturing 2028-2031 | Senior Notes | Qwest Capital Funding, Inc.
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 192		$ 192
Senior Notes Maturing 2028-2031 | Senior Notes | Qwest Capital Funding, Inc. | Minimum
Long-term Debt and Credit Facilities
Stated interest rate	6.875%
Senior Notes Maturing 2028-2031 | Senior Notes | Qwest Capital Funding, Inc. | Maximum
Long-term Debt and Credit Facilities
Stated interest rate	7.75%
Term Loan A-1 | Term Loan
Long-term Debt and Credit Facilities
Long-term debt, weighted average interest rate			7.47%
Revolving Credit Facility | Line of Credit
Long-term Debt and Credit Facilities
Long-term debt, weighted average interest rate			7.464%
10.500% Senior Secured Notes due 2030 | Senior Notes | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Stated interest rate			10.50%