Organization and Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) account	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Property, Plant and Equipment [Line Items]
Commissions expense	$ 5,000,000	$ 6,200,000	$ 5,200,000
Impairment of intangible assets	$ 0	0	0
Number of significant allowance accounts | account	2
Contractor fee, annual percentage increase	2.00%
Uncertain tax positions	$ 0	0
Advertising expenses	1,700,000	2,400,000	2,300,000
Provisions for doubtful accounts, service credits and other	$ 700,000	$ 1,600,000	$ 500,000
Minimum
Property, Plant and Equipment [Line Items]
Useful life	1 year
Maximum
Property, Plant and Equipment [Line Items]
Amortization of intangible assets	10 years
Useful life	5 years
Paging Equipment Assets | Minimum
Property, Plant and Equipment [Line Items]
Useful life	1 year
Paging Equipment Assets | Maximum
Property, Plant and Equipment [Line Items]
Useful life	5 years