Commitments and Contingencies and Other Items (Details) plaintiff in Thousands, $ in Thousands	1 Months Ended	3 Months Ended
	Feb. 28, 2017 USD ($) lawsuit	Mar. 31, 2021 USD ($) Employee plaintiff contract	Dec. 31, 2005 USD ($) subsidiary
Loss Contingencies
Estimate of possible loss		$ 119,000
Patents allegedly infringed | lawsuit	1
Number of members (more than) | plaintiff		12
Unfavorable Regulatory Action
Loss Contingencies
Estimate of possible loss		$ 300
Level 3 Parent, LLC
Loss Contingencies
Damages sought, value		$ 50,000
U.S. District Court for the District of Minnesota
Loss Contingencies
Number of members (more than) | plaintiff		11
Missouri Municipalities | Judicial ruling
Loss Contingencies
Litigation settlement amount	$ 4,000
Minnesota Securities Investor Class Actions | U.S. District Court for the District of Minnesota
Loss Contingencies
Litigation settlement amount		$ 55,000
Peruvian Tax Litigation | Pending litigation
Loss Contingencies
Estimate of possible loss		1,000
Number of subsidiaries issues with tax assessment | subsidiary			1
Loss contingency, asserted claim			$ 26,000
Brazilian Tax Claims | Pending litigation
Loss Contingencies
Loss contingency, range of possible loss, portion not accrued		12,000
Brazilian Tax Claims | Pending litigation | Maximum
Loss Contingencies
Loss contingency, range of possible loss, portion not accrued		$ 49,000
United States of America ex rel., Stephen Bishop v. Level 3 Communications, Inc. et al.
Loss Contingencies
Number of former employees names in lawsuit | Employee		2
Number of government contracts in question | contract		2
Number of former employees with plea agreements | Employee		1