Long-Term Debt and Credit Facilities - Long Term Debt (Details) $ in Millions	12 Months Ended
	Dec. 31, 2024 USD ($) subsidiary	Mar. 31, 2024	Dec. 31, 2023 USD ($)	Apr. 17, 2023
Debt Disclosure [Abstract]
Number of subsidiaries | subsidiary	3
Long-term Debt and Credit Facilities
Finance lease and other obligations	$ 254		$ 285
Unamortized discounts, net	(395)		(4)
Unamortized debt issuance costs	(217)		(145)
Total long-term debt	17,906		19,988
Less current maturities	(412)		(157)
Long-term debt, excluding current maturities	17,494		19,831
Tranche B 2027 Term Loan | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 12		2,411
Line of Credit | Series A Revolving Credit Facility
Long-term Debt and Credit Facilities
Basis spread (as a percent)	4.00%
Long-term debt, gross	$ 0		0
Line of Credit | Series B Revolving Credit Facility
Long-term Debt and Credit Facilities
Basis spread (as a percent)	6.00%
Long-term debt, gross	$ 0		$ 0
Term Loan | Qwest Corporation
Long-term Debt and Credit Facilities
Long-term debt, weighted average interest rate (as a percent)			7.97%
Term Loan | Term Loan A
Long-term Debt and Credit Facilities
Basis spread (as a percent)	6.00%
Long-term debt, gross	$ 357		$ 0
Long-term debt, weighted average interest rate (as a percent)	10.573%		7.464%
Term Loan | Term Loan B-1
Long-term Debt and Credit Facilities
Basis spread (as a percent)	2.35%
Long-term debt, gross	$ 1,606		$ 0
Long-term debt, weighted average interest rate (as a percent)	7.037%
Term Loan | Term Loan B-1 | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Basis spread (as a percent)	6.56%
Long-term debt, gross	$ 1,199		0
Long-term debt, weighted average interest rate (as a percent)	11.133%
Term Loan | Term Loan B-2
Long-term Debt and Credit Facilities
Basis spread (as a percent)	2.35%
Long-term debt, gross	$ 1,606		0
Long-term debt, weighted average interest rate (as a percent)	7.037%
Term Loan | Term Loan B-2 | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Basis spread (as a percent)	6.56%
Long-term debt, gross	$ 1,199		0
Long-term debt, weighted average interest rate (as a percent)	11.133%
Term Loan | Term Loan B
Long-term Debt and Credit Facilities
Basis spread (as a percent)	2.25%
Long-term debt, gross	$ 56		$ 3,891
Long-term debt, weighted average interest rate (as a percent)	6.937%		7.72%
Term Loan | Tranche B 2027 Term Loan | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Basis spread (as a percent)	1.75%
Long-term debt, weighted average interest rate (as a percent)	6.437%		7.22%
Term Loan | Former Term Loan | Qwest Corporation
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 0		$ 215
Term Loan | Term Loan A-1
Long-term Debt and Credit Facilities
Long-term debt, weighted average interest rate (as a percent)			7.47%
Line of Credit and Medium-term Notes | Other Facilities
Long-term Debt and Credit Facilities
Long-term debt, gross	0		$ 1,399
Senior Notes | Superpriority Notes
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 1,247		0
Senior Notes | Superpriority Notes | Minimum
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)	4.125%
Senior Notes | Superpriority Notes | Maximum
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)	10.00%
Senior Notes | Former Parent Secured Notes
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 0		$ 1,250
Long-term debt, weighted average interest rate (as a percent)			4.00%
Senior Notes | First Lien Notes | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 3,846		$ 925
Senior Notes | First Lien Notes | Level 3 Financing, Inc. | Minimum
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)	10.50%
Senior Notes | First Lien Notes | Level 3 Financing, Inc. | Maximum
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)	11.00%
Senior Notes | Second Lien Notes | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 2,579		0
Senior Notes | Second Lien Notes | Level 3 Financing, Inc. | Minimum
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)	3.875%
Senior Notes | Second Lien Notes | Level 3 Financing, Inc. | Maximum
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)	10.00%
Senior Notes | Former Level 3 Senior Notes | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 0		$ 1,500
Senior Notes | Former Level 3 Senior Notes | Level 3 Financing, Inc. | Minimum
Long-term Debt and Credit Facilities
Long-term debt, weighted average interest rate (as a percent)			3.40%
Senior Notes | Former Level 3 Senior Notes | Level 3 Financing, Inc. | Maximum
Long-term Debt and Credit Facilities
Long-term debt, weighted average interest rate (as a percent)			3.875%
Senior Notes | Senior Notes Due 2025-2042
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 1,428		$ 2,143
Senior Notes | Senior Notes Due 2025-2042 | Minimum
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)	4.00%
Senior Notes | Senior Notes Due 2025-2042 | Maximum
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)	7.65%
Senior Notes | Senior Notes Maturing 2027-2029 | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 964		3,940
Senior Notes | Senior Notes Maturing 2027-2029 | Level 3 Financing, Inc. | Minimum
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)	3.40%
Senior Notes | Senior Notes Maturing 2027-2029 | Level 3 Financing, Inc. | Maximum
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)	4.625%
Senior Notes | Senior Notes, Maturing 2025-2057 | Qwest Corporation
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 1,973		1,986
Senior Notes | Senior Notes, Maturing 2025-2057 | Qwest Corporation | Minimum
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)	6.50%
Senior Notes | Senior Notes, Maturing 2025-2057 | Qwest Corporation | Maximum
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)	7.75%
Senior Notes | Senior Notes Maturing 2028 - 2031 | Qwest Capital Funding, Inc.
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 192		$ 192
Senior Notes | Senior Notes Maturing 2028 - 2031 | Qwest Capital Funding, Inc. | Minimum
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)	6.875%
Senior Notes | Senior Notes Maturing 2028 - 2031 | Qwest Capital Funding, Inc. | Maximum
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)	7.75%
Senior Notes | 10.500% Senior Secured Notes due 2030 | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)	10.50%	10.50%		10.50%