Commitments and Contingencies - Additional Information (Details)					3 Months Ended		6 Months Ended
	Jan. 02, 2018 USD ($) ft²	Oct. 01, 2017 USD ($) ft²	Sep. 15, 2014 USD ($) ft²	Jun. 29, 2012 USD ($) ft²	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Commitments And Contingencies Disclosure [Line Items]
Purchase commitment cancellation notice period							30 days
Deposits for letter of credit					$ 300,000		$ 300,000
Rent expense net					600,000	$ 400,000	1,000,000	$ 700,000
Contingent liability for accrual					0		0		$ 0
Facility Leases
Commitments And Contingencies Disclosure [Line Items]
Lease period			5 years	66 months
Area of leased property | ft²			34,400	12,000
Annual lease payments				$ 500,000
Sublease income					0	100,000	100,000	200,000
Sublease expense					$ 0	$ 100,000	$ 100,000	$ 200,000
Additional period of extension in lease contract			3 years
Initial annual lease payments			$ 1,300,000
Increase in lease payments at final year of agreement			$ 1,600,000
Lease commencement period							2015-01
Lease abatement period			3 months
Sublease Agreement
Commitments And Contingencies Disclosure [Line Items]
Lease period		25 months
Area of leased property | ft²	6,000	8,000
Annual lease payments	$ 400,000	$ 300,000
Lease commencement period		Oct. 01, 2017
Lease expiration date		Oct. 31, 2019