Summary of Significant Accounting Policies - Summary of Allowance for Sales Returns (Details) - Allowance for Sales Returns - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	$ 3,282	$ 63	$ 128
Additional Reserve	34	3,250
Applied Sales Return	(3,249)	(31)	(65)
Balance at End of Year	$ 67	$ 3,282	$ 63