Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Allowance for doubtful accounts	$ 146	$ 286
Property and equipment	396	0
Deferred revenue	11	27
Inventories	7,265	12,724
Stock-based compensation	790	1,857
Sales returns accrual	4,343	7,788
Acquisition costs, net of amortization	116	191
Intangible assets	2,230	77
Goodwill	1,009	1,663
HzO investment	1,007	1,483
Capital loss carry-over	184	271
Reserve on note receivable	0	328
Net operating loss carryforward	3,338	21,313
Federal and state credit carryforwards	3,440	2,816
Other liabilities	1,586	1,619
Total gross deferred tax assets	25,861	52,443
Valuation allowance	(1,458)	(1,753)
Total deferred tax assets	24,403	50,690
Deferred tax liabilities:
Property and equipment	0	323
Other	0	4
Total gross deferred tax liabilities	0	327
Net deferred tax assets	$ 24,403	$ 50,363