Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Commitments And Contingencies [Line Items]
Operating leases, rent expense	$ 3,311	$ 3,292	$ 3,296
Lease agreements expiration year	2029
Operating leases, equipment	$ 98	111	99
Operating leases, future minimum payments due	3,170
Operating leases, future minimum payments, due in two years	2,801
Operating leases, future minimum payments, due in three years	2,107
Operating leases, future minimum payments, due in four years	2,051
Operating leases, future minimum payments, due in five years	1,725
Operating leases, future minimum payments, due thereafter	7,484
Royalty expense	1,904	$ 1,117	$ 586
Purchase commitment, remaining minimum amount committed	$ 71,752
Percentage of maximum borrowing capacity of value of eligible securities	70.00%
Available line of credit	$ 93,920
Available interest rate on line of credit	4.00%
Equipment [Member]
Commitments And Contingencies [Line Items]
Lease agreements expiration year	2023
Minimum [Member]
Commitments And Contingencies [Line Items]
Warranty period	12 months
Maximum [Member]
Commitments And Contingencies [Line Items]
Warranty period	15 months