Adoption of New Accounting Policy - Impact on Statements of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue:
Revenue	$ 54,418	$ 32,731	$ 146,960	$ 90,145
Cost of revenue, exclusive of depreciation and amortization shown below:
Cost of revenue, exclusive of depreciation and amortization	35,058	23,465	99,132	64,088
Loss from operations	9,810	(773)	(40,396)	(4,636)
Net income	10,416	6,165	(36,704)	1,889
Net income attributable to common stockholders:
Net income (loss) attributable to common stockholders, basic	10,416	6,165	(36,704)	1,889
Net income (loss) attributable to common stockholders, diluted	$ 10,416	$ 6,165	$ (36,704)	$ 1,889
Net income (loss) per share attributable to common stockholders, basic (in dollars per share)	$ 0.54	$ 0.37	$ (1.93)	$ 0.11
Net income (loss) per share attributable to common stockholders, diluted (in dollars per share)	$ 0.47	$ 0.33	$ (1.93)	$ 0.10
As Previously Reported | ASU 2014-09
Revenue:
Revenue		$ 33,268		$ 90,613
Cost of revenue, exclusive of depreciation and amortization shown below:
Cost of revenue, exclusive of depreciation and amortization		23,465		64,088
Loss from operations		(236)		(4,168)
Net income		7,695		3,350
Net income attributable to common stockholders:
Net income (loss) attributable to common stockholders, basic		7,695		3,350
Net income (loss) attributable to common stockholders, diluted		$ 7,695		$ 3,350
Net income (loss) per share attributable to common stockholders, basic (in dollars per share)		$ 0.46		$ 0.20
Net income (loss) per share attributable to common stockholders, diluted (in dollars per share)		$ 0.41		$ 0.18
Adjustment for ASU on Revenue Recognition | ASU 2014-09
Revenue:
Revenue		$ (537)		$ (468)
Cost of revenue, exclusive of depreciation and amortization shown below:
Loss from operations		(537)		(468)
Net income		(1,530)		(1,461)
Net income attributable to common stockholders:
Net income (loss) attributable to common stockholders, basic		(1,530)		(1,461)
Net income (loss) attributable to common stockholders, diluted		$ (1,530)		$ (1,461)
Net income (loss) per share attributable to common stockholders, basic (in dollars per share)		$ (0.09)		$ (0.09)
Net income (loss) per share attributable to common stockholders, diluted (in dollars per share)		$ (0.08)		$ (0.08)
Product
Revenue:
Revenue	$ 28,045	$ 23,780	$ 82,603	$ 68,995
Cost of revenue, exclusive of depreciation and amortization shown below:
Cost of revenue, exclusive of depreciation and amortization	21,100	18,418	62,007	53,151
Product | As Previously Reported | ASU 2014-09
Revenue:
Revenue		24,621		71,391
Cost of revenue, exclusive of depreciation and amortization shown below:
Cost of revenue, exclusive of depreciation and amortization		18,979		54,847
Product | Adjustment for ASU on Revenue Recognition | ASU 2014-09
Revenue:
Revenue		(841)		(2,396)
Cost of revenue, exclusive of depreciation and amortization shown below:
Cost of revenue, exclusive of depreciation and amortization		(561)		(1,696)
Service
Revenue:
Revenue	26,373	8,951	64,357	21,150
Cost of revenue, exclusive of depreciation and amortization shown below:
Cost of revenue, exclusive of depreciation and amortization	$ 13,958	5,047	$ 37,125	10,937
Service | As Previously Reported | ASU 2014-09
Revenue:
Revenue		8,647		19,222
Cost of revenue, exclusive of depreciation and amortization shown below:
Cost of revenue, exclusive of depreciation and amortization		4,486		9,241
Service | Adjustment for ASU on Revenue Recognition | ASU 2014-09
Revenue:
Revenue		304		1,928
Cost of revenue, exclusive of depreciation and amortization shown below:
Cost of revenue, exclusive of depreciation and amortization		$ 561		$ 1,696