Long-Term Debt and Credit Facilities - Subsequent Events (Details) - Subsequent Event - USD ($)	Feb. 16, 2021	Feb. 12, 2021	Jan. 13, 2021
Level 3 Financing, Inc. | Senior Notes | 5.375% Senior Notes Due 2022
Long-term Debt and Credit Facilities
Amount of debt redeemed		$ 900,000,000
Interest rate, stated percentage		0.05375%
Level 3 Financing, Inc. | Senior Notes | 3.750 Sustainability-Linked Senior Notes Due 2029
Long-term Debt and Credit Facilities
Debt instrument, face amount			$ 900,000,000
Interest rate, stated percentage			3.75%
Qwest Corporation | Senior Notes | 7.000% Senior Notes Due 2056
Long-term Debt and Credit Facilities
Amount of debt redeemed	$ 235,000,000
Interest rate, stated percentage	7.00%