Commitments and Contingencies - Additional Information (Details) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2015 USD ($)	Dec. 31, 2016 USD ($) agreement	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Commitments And Contingencies [Line Items]
Number of exclusive agreements | agreement		2
Rent expense		$ 17.9	$ 18.5	$ 19.3
Minimum
Commitments And Contingencies [Line Items]
LOC contract period requirement		1 year
Operating leases, term of contract		1 month
Maximum
Commitments And Contingencies [Line Items]
LOC contract period requirement		3 years
Operating leases, term of contract		5 years
Paging Equipment Assets
Commitments And Contingencies [Line Items]
Long-term purchase commitment	$ 10.2	$ 4.0