Consolidated Financial Statement Components - Property and Equipment, Net (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 96,794	$ 98,061
Accumulated depreciation	(88,992)	(89,838)
Total property and equipment, net	7,802	8,223
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment	2,497	2,497
Asset retirement costs
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 3,848	3,848
Asset retirement costs | Minimum
Property, Plant and Equipment [Line Items]
Useful Life (In Years)	1 year
Asset retirement costs | Maximum
Property, Plant and Equipment [Line Items]
Useful Life (In Years)	5 years
Paging and computer equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 87,224	88,427
Paging and computer equipment | Minimum
Property, Plant and Equipment [Line Items]
Useful Life (In Years)	1 year
Paging and computer equipment | Maximum
Property, Plant and Equipment [Line Items]
Useful Life (In Years)	5 years
Furniture, fixtures and vehicles
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 3,225	$ 3,289
Furniture, fixtures and vehicles | Minimum
Property, Plant and Equipment [Line Items]
Useful Life (In Years)	3 years
Furniture, fixtures and vehicles | Maximum
Property, Plant and Equipment [Line Items]
Useful Life (In Years)	5 years