Long-Term Debt and Credit Facilities - Schedule of Long Term Debt (Details) - USD ($) $ in Millions		12 Months Ended
	Nov. 27, 2019	Dec. 31, 2023	Dec. 31, 2022
Long-term Debt and Credit Facilities
Finance lease and other obligations		$ 285	$ 317
Unamortized discounts, net		(4)	(7)
Unamortized debt issuance costs		(145)	(169)
Total long-term debt		19,988	20,572
Less current maturities		(157)	(154)
Long-term debt, excluding current maturities		19,831	20,418
Credit Facility | Revolving Credit Facility
Long-term Debt and Credit Facilities
Long-term debt, gross		$ 200	0
Long-term debt, weighted average interest rate (as a percent)		7.464%
Credit Facility | Revolving Credit Facility | SOFR
Long-term Debt and Credit Facilities
Basis spread (as a percent)		2.00%
Term Loan | Term Loan A
Long-term Debt and Credit Facilities
Long-term debt, gross		$ 933	$ 991
Long-term debt, weighted average interest rate (as a percent)		7.47%	6.384%
Term Loan | Term Loan A | SOFR
Long-term Debt and Credit Facilities
Basis spread (as a percent)		2.00%
Term Loan | Term Loan A-1
Long-term Debt and Credit Facilities
Long-term debt, gross		$ 266	$ 283
Long-term debt, weighted average interest rate (as a percent)		7.47%	6.384%
Term Loan | Term Loan A-1 | SOFR
Long-term Debt and Credit Facilities
Basis spread (as a percent)		2.00%
Term Loan | Term Loan B
Long-term Debt and Credit Facilities
Long-term debt, gross		$ 3,891	$ 3,941
Long-term debt, weighted average interest rate (as a percent)		7.72%	6.634%
Term Loan | Term Loan B | SOFR
Long-term Debt and Credit Facilities
Basis spread (as a percent)		2.25%
Senior Notes | Senior Notes Due 2027
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)		4.00%
Long-term debt, gross		$ 1,250	$ 1,250
Senior Notes | Senior Notes Due 2025-2042
Long-term Debt and Credit Facilities
Long-term debt, gross		$ 2,143	3,722
Senior Notes | Senior Notes Due 2025-2042 | Minimum
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)		4.50%
Senior Notes | Senior Notes Due 2025-2042 | Maximum
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)		7.65%
Level 3 Financing, Inc. | Term Loan | Tranche B 2027 Term Loan
Long-term Debt and Credit Facilities
Long-term debt, gross		$ 2,411	$ 2,411
Long-term debt, weighted average interest rate (as a percent)		7.22%	6.134%
Level 3 Financing, Inc. | Term Loan | Tranche B 2027 Term Loan | SOFR
Long-term Debt and Credit Facilities
Basis spread (as a percent)	1.00%	1.75%
Level 3 Financing, Inc. | Senior Notes | Senior Notes Due 2027-2030
Long-term Debt and Credit Facilities
Long-term debt, gross		$ 2,425	$ 1,500
Level 3 Financing, Inc. | Senior Notes | Senior Notes Due 2027-2030 | Minimum
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)		3.40%
Level 3 Financing, Inc. | Senior Notes | Senior Notes Due 2027-2030 | Maximum
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)		10.50%
Level 3 Financing, Inc. | Senior Notes | Senior Notes Due 2027-2029
Long-term Debt and Credit Facilities
Long-term debt, gross		$ 3,940	3,940
Level 3 Financing, Inc. | Senior Notes | Senior Notes Due 2027-2029 | Minimum
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)		3.625%
Level 3 Financing, Inc. | Senior Notes | Senior Notes Due 2027-2029 | Maximum
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)		4.625%
Qwest Corporation | Term Loan
Long-term Debt and Credit Facilities
Long-term debt, gross		$ 215	$ 215
Long-term debt, weighted average interest rate (as a percent)		7.97%	6.64%
Qwest Corporation | Term Loan | SOFR
Long-term Debt and Credit Facilities
Basis spread (as a percent)		2.50%
Qwest Corporation | Senior Notes
Long-term Debt and Credit Facilities
Long-term debt, gross		$ 1,986	$ 1,986
Qwest Corporation | Senior Notes | Minimum
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)		6.50%
Qwest Corporation | Senior Notes | Maximum
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)		7.75%
Qwest Capital Funding, Inc. | Senior Notes
Long-term Debt and Credit Facilities
Long-term debt, gross		$ 192	$ 192
Qwest Capital Funding, Inc. | Senior Notes | Minimum
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)		6.875%
Qwest Capital Funding, Inc. | Senior Notes | Maximum
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)		7.75%