Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Deferred tax assets:
Accounts receivable, due to allowance for doubtful accounts	$ 641	$ 313
Inventories	436	289
Operating loss carry-forwards	1,392	1,011
Stock-based compensation expense	1,515	1,194
Intangible assets due to differences in amortization	0	74
Research and development, alternative minimum tax credit carry-forwards	2,600	3,507
Foreign tax credit carry-forwards	1,442	1,111
State tax credit carry-forwards	2,094	2,228
Accrued expenses	722	688
Gross deferred tax assets	10,842	10,415
Less valuation allowance	(2,700)	(2,136)
Total deferred tax assets	8,142	8,279
Deferred tax liabilities:
Purchased intangible assets	(3,129)	(433)
Property and equipment, due to differences in depreciation	(2,548)	(3,176)
Other	(30)	0
Total deferred tax liabilities	(5,707)	(3,609)
Net deferred tax assets	2,435	4,670
Net deferred tax asset—current	3,060	1,146
Deferred Tax Assets, Gross, Noncurrent	0	3,524
Net deferred tax liability—noncurrent	$ (625)	$ 0