Consolidated Financial Statements' Components - Depreciation, Amortization and Accretion (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Total depreciation	$ 4,056	$ 5,012	$ 6,197
Intangible assets	417	2,500	2,500
Capitalized software development costs	5,357	1,073	0
Total amortization	5,774	3,573	2,500
Accretion	616	471	552
Total depreciation, amortization and accretion expense	10,446	9,056	9,249
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total depreciation	88	57	63
Asset retirement costs
Property, Plant and Equipment [Line Items]
Total depreciation	87	643	766
Paging and computer equipment
Property, Plant and Equipment [Line Items]
Total depreciation	3,797	5,291	6,526
Furniture, fixtures and vehicles
Property, Plant and Equipment [Line Items]
Total depreciation	$ 258	$ 307	$ 374