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Goodwill and Intangible Assets, Net - Narrative (Details) - USD ($)			9 Months Ended	12 Months Ended
	Mar. 08, 2017	Jan. 01, 2017	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill acquired				$ 0	$ 38,868,000
Goodwill impairment			$ 0	0	0	$ 0
Amortization				15,219,000	12,282,000	1,800,000
Impairment of long-lived assets				0	$ 0	$ 0
ObjectVideo
Goodwill [Line Items]
Goodwill acquired		$ 2,300,000
Connect And Piper
Goodwill [Line Items]
Goodwill acquired	$ 36,600,000
EnergyHub
Goodwill [Line Items]
Accumulated balance of goodwill impairments				$ 4,800,000