Commitments and Contingencies - Additional Information (Detail) - Procurement Agreement [Member] - Europe [Member] - Airtime [Member] - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2001
Long Term Purchase Commitment [Line Items]
Credits provided			$ 3,736
Credits used	$ 7	$ 7
Unused credits granted	$ 1,941	$ 1,971

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration