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Commitments and Contingencies - Additional Information (Detail) - USD ($)
$ in Millions
1 Months Ended 12 Months Ended
Mar. 31, 2014
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Commitments And Contingencies [Line Items]        
Deposits related to letter of credit are included in other assets   $ 0.3    
Rent expense   $ 18.5 $ 18.6 $ 19.1
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]        
Term of purchase commitment 3 years      
Long-term purchase commitment $ 8.3 $ 5.7