Acquisition - Narrative (Details) - 3M's Drive-Thru Communications Systems $ in Thousands	Sep. 30, 2019 USD ($)
Business Acquisition [Line Items]
Business acquisition, purchase price	$ 8,400
Fair value of assets acquired	8,412
Warranty liability assumed	1,412
Business acquisition, cash paid	7,000
Warranty liability assumed, short-term	712
Warranty liability assumed, long-term	$ 700

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Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Assets Acquired Including Goodwill

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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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