Long-Term Debt and Credit Facilities - Long Term Debt (Details)	6 Months Ended
	Jun. 30, 2024 USD ($) subsidiary	Mar. 31, 2024	Dec. 31, 2023 USD ($)
Debt Disclosure [Abstract]
Number of subsidiaries | subsidiary	3
Long-term Debt and Credit Facilities
Finance lease and other obligations	$ 270,000,000		$ 285,000,000
Unamortized discounts, net	(476,000,000)		(4,000,000)
Unamortized debt issuance costs	(235,000,000)		(145,000,000)
Total long-term debt	18,603,000,000		19,988,000,000
Less current maturities	(192,000,000)		(157,000,000)
Long-term debt, excluding current maturities	$ 18,411,000,000		19,831,000,000
Term Loan | Qwest Corporation
Long-term Debt and Credit Facilities
Basis spread (as a percent)	2.50%
Long-term debt, gross	$ 0		$ 215,000,000
Long-term debt, weighted average interest rate			7.97%
Series A Revolving Credit Facility | Line of Credit
Long-term Debt and Credit Facilities
Basis spread (as a percent)	4.00%
Long-term debt, gross	$ 0		$ 0
Series B Revolving Credit Facility | Line of Credit
Long-term Debt and Credit Facilities
Basis spread (as a percent)	6.00%
Long-term debt, gross	$ 0		0
Term Loan A | Term Loan
Long-term Debt and Credit Facilities
Basis spread (as a percent)	6.00%
Long-term debt, gross	$ 368,000,000		$ 0
Long-term debt, weighted average interest rate	11.344%		7.464%
Term Loan B-1 | Term Loan
Long-term Debt and Credit Facilities
Basis spread (as a percent)	2.35%
Long-term debt, gross	$ 1,621,000,000		$ 0
Long-term debt, weighted average interest rate	7.808%
Term Loan B-1 | Term Loan | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Basis spread (as a percent)	6.56%
Long-term debt, gross	$ 1,199,000,000		0
Long-term debt, weighted average interest rate	11.904%
Term Loan B-2 | Term Loan
Long-term Debt and Credit Facilities
Basis spread (as a percent)	2.35%
Long-term debt, gross	$ 1,621,000,000		0
Long-term debt, weighted average interest rate	7.808%
Term Loan B-2 | Term Loan | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Basis spread (as a percent)	6.56%
Long-term debt, gross	$ 1,199,000,000		0
Long-term debt, weighted average interest rate	11.904%
Term Loan B | Term Loan
Long-term Debt and Credit Facilities
Basis spread (as a percent)	2.25%
Long-term debt, gross	$ 57,000,000		$ 3,891,000,000
Long-term debt, weighted average interest rate	7.708%		7.72%
Other Facilities | Line of Credit and Term Loan
Long-term Debt and Credit Facilities
Basis spread (as a percent)	2.00%
Long-term debt, gross	$ 0		$ 1,399,000,000
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	$ 812,000,000		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		1,250,000,000
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, gross	$ 12,000,000		$ 2,411,000,000
Tranche B 2027 Term Loan | Term Loan | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Long-term debt, weighted average interest rate	7.208%		7.22%
First Lien Notes | Senior Notes | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 3,846,000,000		$ 925,000,000
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	$ 2,229,000,000		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		1,500,000,000
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	$ 2,037,000,000		2,143,000,000
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	$ 1,865,000,000		3,940,000,000
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	$ 1,986,000,000		1,986,000,000
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	$ 192,000,000		$ 192,000,000
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%
10.500% Senior Secured Notes due 2030 | Senior Notes | Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Stated interest rate	10.50%