Lease Arrangements - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Lessor Lease Description [Line Items]
Allowance for credit losses for our investment in sales type leases	$ 0	$ 0
Minimum [Member]
Lessor Lease Description [Line Items]
Lessor sales type lease arrangement terms for network equipments	18 months
Maximum [Member]
Lessor Lease Description [Line Items]
Lessor sales type lease arrangement terms for network equipments	5 years