Long-Term Debt and Credit Facilities - 2026 Debt Transactions - Repurchases of Debt Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2026	Feb. 02, 2026	Jan. 09, 2026
Long-term Debt and Credit Facilities
Principal Amount Repurchased	$ 5	$ 4,765
Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Principal Amount Repurchased			$ 607
Senior Notes \| 4.125% Superpriority Senior Secured Notes Due 2029
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)		4.125%
Principal Amount Repurchased		$ 331
Senior Notes \| 4.125% Superpriority Senior Secured Notes Due 2030
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)		4.125%
Principal Amount Repurchased		$ 477
Senior Notes \| 10.000% Secured Notes due 2032
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)		10.00%
Principal Amount Repurchased		$ 439
Senior Notes \| 4.875% Second Lien Notes due 2029 \| Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)	4.875%		4.875%
Principal Amount Repurchased	$ 1		$ 595
Senior Notes \| 6.875% Senior Notes due 2028 \| Qwest Corporation
Long-term Debt and Credit Facilities
Stated interest rate (as a percent)	6.875%
Principal Amount Repurchased	$ 4
Term Loan \| Superpriority Term Loan A
Long-term Debt and Credit Facilities
Principal Amount Repurchased		338
Term Loan \| Superpriority Term Loan B-1
Long-term Debt and Credit Facilities
Principal Amount Repurchased		1,590
Term Loan \| Superpriority Term Loan B-2
Long-term Debt and Credit Facilities
Principal Amount Repurchased		$ 1,590