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Leases - Additional Information (Detail) - USD ($)
 3 Months Ended 9 Months Ended
Sep. 30, 2019
Sep. 30, 2019
Dec. 31, 2018
Lessor and Lessee Lease Description [Line Items]      
Operating lease, option to extend, existence   true  
Operating lease, option to terminate, existence   true  
Short-term lease cost $ 100,000 $ 300,000  
Variable lease cost 300,000 700,000  
Future operating lease payments 20,812,000 20,812,000 $ 7,600,000
Allowance for credit losses for our investment in sales type leases $ 0 $ 0 $ 0
Minimum [Member]      
Lessor and Lessee Lease Description [Line Items]      
Operating lease, remaining lease terms   2 months  
Operating lease, options to terminate term   3 months  
Maximum [Member]      
Lessor and Lessee Lease Description [Line Items]      
Operating lease, remaining lease terms   6 years  
Operating lease, renewal term 5 years 5 years  
Lessor sales type lease arrangement terms for network equipments   5 years