Long-Term Debt and Credit Facilities - Repayments and Exchanges (Details) $ in Millions	3 Months Ended
	Mar. 31, 2024 USD ($)
Long-term Debt and Credit Facilities
Repayment	$ 2,258
Exchange	10,244
Term Loan | Term Loan A
Long-term Debt and Credit Facilities
Repayment	933
Exchange	0
Term Loan | Term Loan A-1
Long-term Debt and Credit Facilities
Repayment	266
Exchange	0
Term Loan | Term Loan B
Long-term Debt and Credit Facilities
Repayment	575
Exchange	$ 3,259
Senior Notes | 5.125% Senior Notes Due 2026
Long-term Debt and Credit Facilities
Stated interest rate	5.125%
Repayment	$ 116
Exchange	$ 147
Senior Notes | 4.000% Senior Notes Due 2027
Long-term Debt and Credit Facilities
Stated interest rate	4.00%
Repayment	$ 153
Exchange	865
Level 3 Financing, Inc. | Term Loan | Term Loan B
Long-term Debt and Credit Facilities
Repayment	0
Exchange	$ 2,398
Level 3 Financing, Inc. | Senior Notes | 3.400% Senior Notes Due 2027
Long-term Debt and Credit Facilities
Stated interest rate	3.40%
Repayment	$ 0
Exchange	$ 668
Level 3 Financing, Inc. | Senior Notes | 3.875% Senior Notes Due 2029
Long-term Debt and Credit Facilities
Stated interest rate	3.875%
Repayment	$ 0
Exchange	$ 678
Level 3 Financing, Inc. | Senior Notes | 4.625% Senior Notes Due 2027
Long-term Debt and Credit Facilities
Stated interest rate	4.625%
Repayment	$ 0
Exchange	$ 606
Level 3 Financing, Inc. | Senior Notes | 4.250% Senior Notes Due 2028
Long-term Debt and Credit Facilities
Stated interest rate	4.25%
Repayment	$ 0
Exchange	$ 712
Level 3 Financing, Inc. | Senior Notes | 3.625% Senior Notes Due 2029
Long-term Debt and Credit Facilities
Stated interest rate	3.625%
Repayment	$ 0
Exchange	$ 458
Level 3 Financing, Inc. | Senior Notes | 3.750% Senior Notes Due 2029
Long-term Debt and Credit Facilities
Stated interest rate	3.75%
Repayment	$ 0
Exchange	453
Qwest Corporation | Term Loan
Long-term Debt and Credit Facilities
Repayment	215
Exchange	$ 0