Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Components of Deferred Tax Assets and Liabilities [Abstract]
Accrued liabilities	$ 3,000	$ 5,089
Allowance for doubtful accounts	12	40
Inventory valuation	254	199
Capitalized indirect inventory costs	383	497
Stock-based compensation expense	897	1,346
Deferred rent	588	865
Accrued royalty	0	429
Net operating loss carryforward	1,715	2,377
Basis difference on long-lived assets	548	1,052
Credit carryforward	634	615
Other	179	140
Total deferred income tax assets before valuation allowance	8,210	12,649
Valuation allowance	(914)	(886)
Total deferred income tax assets, net of valuation allowance	7,296	11,763
Prepaid advertising	(370)	(1,302)
Other prepaids	(610)	(744)
Basis difference of long-lived assets	(14,856)	(26,215)
Undistributed earnings of foreign subsidiaries	0	(457)
Other	(18)	(25)
Deferred income tax liabilities	(15,854)	(28,743)
Net deferred income tax liabilities	(8,558)	$ (16,980)
Domestic Tax Authority [Member] | Loss and Other Credit Carryforward [Member]
Components of Deferred Tax Assets and Liabilities [Abstract]
Valuation allowance	$ (700)