Summary of Significant Accounting Policies - Summary (Details)		3 Months Ended
	Jan. 01, 2020 USD ($)	Mar. 31, 2020 USD ($) item segment	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Segments
Number of business activities | item		1
Number of operating segments | segment		1
Foreign Currency Translation
Foreign currency translation gain		$ 1,169,000	$ 64,000
(Gain) loss from foreign currency translation adjustments		2,000,000.0
Unrealized foreign currency losses		2,024,000	87,000
Trading Securities
Trading securities		0		$ 0
Restricted cash
Restricted cash pledged for letter of credit		8,800,000	8,800,000	8,800,000
Cash and cash equivalents		53,614,000		62,430,000
Restricted cash		9,326,000		9,326,000
cash, cash equivalents and restricted cash in the condensed consolidated statements of cash flows		$ 62,940,000	42,493,000	71,756,000	$ 38,596,000
Number of Months from start of lease for adjustments to Letter of Credit | item		37
Frequency of adjustment to Letter of Credit		12 months
Adjustment rate of Letter of Credit (as a percent)		20.00%
Amount of Letter of Credit outstanding after adjustments		$ 2,000,000.0
Number of other irrevocable letters of credit outstanding | item		2
Restricted cash pledged for office lease agreement		$ 400,000
Restricted cash pledged for credit card program		200,000
Accounts Receivable
Allowance for doubtful accounts receivable		1,587,000		1,240,000
Inventory
Inventory write-down		7,900,000
Long Lived Assets
Long-lived asset impairment		$ 0	$ 0
Revenue Recognition
Practical expedient of transaction prices allocated to remaining performance obligations		true
Practical expedient cost of obtaining contract		true
Number of performance obligations that exist for majority of the contracts with customers | item		1
Warranty period from date of shipment		1 year
Retained earnings		$ (243,768,000)		$ (189,710,000)
Adjustment | ASU 2016-13
Revenue Recognition
Retained earnings	$ 0
Adjustment | ASU 2018-15
Revenue Recognition
Costs capitalized relating to global enterprise systems	$ 1,600,000
Minimum
Long Lived Assets
Estimated useful lives of assets		3 years
Intangible Assets
Useful life/amortization period		5 years
Maximum
Long Lived Assets
Estimated useful lives of assets		5 years
Intangible Assets
Useful life/amortization period		11 years