Organization and Significant Accounting Policies - Additional Information (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2016 USD ($) account message	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Property, Plant and Equipment [Line Items]
Monthly messages sent through company solutions (over 100 million messages) | message		100,000,000
Deferred tax assets	$ 79,994	$ 73,068	$ 79,994
Deferred income tax (benefit) expense		6,926	(55,018)	$ 4,740
Impairment of intangible assets		$ 0	0
Number of significant allowance accounts | account		2
Allowances for doubtful accounts	1,300	$ 1,100	1,300
Contractor fee, annual percentage increase		4.00%
Commissions expense		$ 5,600	7,200	8,500
Advertising expenses		$ 1,800	1,700	$ 2,300
Minimum
Property, Plant and Equipment [Line Items]
Amortization of intangible assets		2 years
Estimated useful life		1 year
Maximum
Property, Plant and Equipment [Line Items]
Amortization of intangible assets		10 years
Estimated useful life		5 years
Restructuring costs
Property, Plant and Equipment [Line Items]
Advertising expenses			700
Paging Equipment Assets | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life		1 year
Paging Equipment Assets | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life		5 years
Net Operating Loss Carryforward Overstatement | Adjustment
Property, Plant and Equipment [Line Items]
Deferred tax assets	4,300		4,300
Deferred income tax (benefit) expense	$ 4,000		$ 4,000