Balance Sheet Components - Schedule of Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Accounts payable	$ 14,499	$ 13,720
Accrued inventory (in-transit and unvouchered receipts) and trade payables	7,060	9,597
Accrued purchasing card liability	1,738	2,089
Accrued franchise, sales and use taxes	584	518
Other accrued expenses	850	862
Accounts payable and accrued expenses	$ 24,731	$ 26,786