Long-Term Debt and Credit Facilities - Transaction Support Agreement Transactions - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Long-term Debt and Credit Facilities
Aggregate principal		$ 744
Net (loss) gain on early retirement of debt	$ 275	348	$ 618	$ 214
Reduction in debt from fair value adjustment		492
Payment for lender fees		209
Payment for third-party costs		174
Debt instrument, capitalized lender fees		52
Third party costs capitalized		62
Gain (Loss) On Extinguishment Of Debt
Long-term Debt and Credit Facilities
Debt instrument, lender fees		157
Selling, General and Administrative Expenses
Long-term Debt and Credit Facilities
Debt instrument, third-party costs		112
Level 3 Financing, Inc.
Long-term Debt and Credit Facilities
Aggregate principal		$ 2,600