Long-Term Debt and Credit Facilities - Amended and Restated Credit Agreement (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 32,152,000,000
Gain (loss) on extinguishment of debt		$ 72,000,000
Amended Credit Agreement | Minimum | Base Rate
Long-term Debt and Credit Facilities
Interest rate margin	1.50%
Amended Credit Agreement | Minimum | Eurodollar
Long-term Debt and Credit Facilities
Interest rate margin	0.50%
Amended Credit Agreement | Maximum | Base Rate
Long-term Debt and Credit Facilities
Interest rate margin	2.25%
Amended Credit Agreement | Maximum | Eurodollar
Long-term Debt and Credit Facilities
Interest rate margin	1.25%
Revolving Credit Facility | the Revolving Credit Facility
Long-term Debt and Credit Facilities
Long-term debt, gross	$ 2,200,000,000
Revolving Credit Facility | the Revolving Credit Facility | CenturyLink Escrow, LLC | Swingline Loan
Long-term Debt and Credit Facilities
Maximum borrowing capacity	250,000,000
Revolving Credit Facility | the Revolving Credit Facility | CenturyLink Escrow, LLC | Letter of Credit
Long-term Debt and Credit Facilities
Maximum borrowing capacity	800,000,000
Revolving Credit Facility | Term Loan A-1
Long-term Debt and Credit Facilities
Long-term debt, gross	316,000,000
Revolving Credit Facility | Term Loan B
Long-term Debt and Credit Facilities
Long-term debt, gross	4,950,000,000
Term loan | Term Loan A
Long-term Debt and Credit Facilities
Long-term debt, gross	1,108,000,000
Senior Notes
Long-term Debt and Credit Facilities
Gain (loss) on extinguishment of debt	(109,000,000)
Senior Notes | Amended Credit Agreement
Long-term Debt and Credit Facilities
Gain (loss) on extinguishment of debt	$ (67,000,000)
Senior Notes | Amended Credit Agreement, Term Loan B | Base Rate
Long-term Debt and Credit Facilities
Interest rate margin	1.25%
Senior Notes | Amended Credit Agreement, Term Loan B | Eurodollar
Long-term Debt and Credit Facilities
Interest rate margin	2.25%