SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Major Classes of Assets and Liabilities (Details) $ in Thousands	Sep. 30, 2021 USD ($)
Components of discontinued operations reported in the condensed consolidated balance sheet
Current assets	$ 25,990
Current liabilities	90
Held for sale | Assets of non-core, rural ILEC business located in Ohio
Components of discontinued operations reported in the condensed consolidated balance sheet
Current assets	190
Property, plant and equipment	9,473
Goodwill	16,327
Total assets	25,990
Current liabilities	83
Other long-term liabilities	7
Total liabilities	$ 90