Commitments and Contingencies and Other Items (Details) plaintiff in Thousands, $ in Thousands	1 Months Ended	9 Months Ended
	Feb. 28, 2017 USD ($) lawsuit	Sep. 30, 2020 USD ($) subsidiary plaintiff Employee contract	Dec. 31, 2005 USD ($) subsidiary
Loss Contingencies
Estimate of possible loss		$ 129,000
Patents allegedly infringed | lawsuit	1
Unfavorable Regulatory Action
Loss Contingencies
Estimate of possible loss		100
Level 3 Parent, LLC
Loss Contingencies
Damages sought, value		50,000
U.S. District Court for the District of Minnesota
Loss Contingencies
Litigation settlement amount		15,500
Litigation settlement, expense		$ 3,500
Number of members (more than) | plaintiff		12
Missouri municipalities | Judicial ruling
Loss Contingencies
Litigation settlement amount	$ 4,000
Peruvian Tax Litigation | Pending litigation
Loss Contingencies
Estimate of possible loss		$ 3,000
Number of subsidiaries issues with tax assessment | subsidiary			1
Loss contingency, asserted claim			$ 26,000
Brazilian Tax Claims | Pending litigation
Loss Contingencies
Number of subsidiaries issues with tax assessment | subsidiary		1
Loss contingency, range of possible loss, portion not accrued		$ 16,000
Brazilian Tax Claims | Pending litigation | Maximum
Loss Contingencies
Loss contingency, range of possible loss, portion not accrued		$ 44,000
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