Accounts Receivable, Net and Revenue Concentrations - Accounts Receivable, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Accounts Receivable, after Allowance for Credit Loss, Current [Abstract]
Trade receivables, gross	$ 150,779	$ 133,774
Allowance for doubtful accounts	(1,122)	(1,121)	$ (1,008)	$ (1,064)
Allowance for sales returns	(582)	(731)
Net trade receivables	149,075	131,922
Other	5,558	12,767
Accounts receivable, net	$ 154,633	$ 144,689