Long-Term Debt and Credit Facilities - Credit Facilities Transactions (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 27, 2025	Dec. 31, 2024
Long-term Debt and Credit Facilities
Net (loss) gain on early retirement of debt	$ (35)	$ 275
Level 3 Financing, Inc. | Term Loan B-3 | Term Loan
Long-term Debt and Credit Facilities
Long-term debt, gross	2,400		$ 2,400	$ 0
Net (loss) gain on early retirement of debt	$ (35)