Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net (loss) income	$ (7,517)	$ 2,253	$ 41
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Provision for doubtful accounts	872	1,337	1,610
Depreciation and amortization	12,564	12,719	9,987
Deferred income taxes	2,406	(411)	(1,813)
Loss (gain) on sale of fixed assets	907	(4)	30
Unrealized gain (loss) on derivative instruments	0	57	0
Compensation expense related to stock-based awards and employee stock purchase plan	3,651	3,734	3,771
Foreign Currency Transaction Gain (Loss), Unrealized	881	391	0
Changes in operating assets and liabilities:
Accounts receivable	10,709	(5,803)	(8,235)
Inventories	806	(3,755)	867
Prepaid expenses and other current assets	(332)	(1,576)	1,141
Other non-current assets	(2,378)	1,539	569
Accounts payable	(790)	(3,390)	1,676
Deferred revenue	1,474	(1,643)	1,622
Accrued expenses	(3,687)	3,023	(1,002)
Other long-term liabilities	(867)	(74)	106
Net cash provided by operating activities	18,699	8,397	10,370
Cash flows from investing activities:
Capital expenditures	(5,631)	(5,694)	(5,118)
Net cash paid for business acquired	0	0	(43,448)
Purchases of marketable securities	(13,173)	(11,323)	(12,270)
Maturities and sales of marketable securities	10,080	13,217	34,150
Net cash used in investing activities	(8,724)	(3,800)	(26,686)
Cash flows from financing activities:
Repayments of long-term debt	(1,358)	(1,307)	(1,272)
Repayments of Long-term loan	(5,281)	(4,876)	(1,219)
Proceeds from Long-term loan	0	0	65,000
Proceeds from stock options exercised and employee stock purchase plan	2,583	432	608
Payment of employee restricted stock withholdings	(313)	(578)	(482)
Repayments of line of credit borrowings	0	0	(30,000)
Other	(4)	0	41
Net cash (used in) provided by financing activities	(4,373)	(6,329)	32,676
Effect of exchange rate changes on cash and cash equivalents	(1,899)	(838)	(429)
Net increase in cash and cash equivalents	3,703	(2,570)	15,931
Cash and cash equivalents at beginning of period	22,719	25,289	9,358
Cash and cash equivalents at end of period	26,422	22,719	25,289
Supplemental disclosure of cash flow information:
Cash paid for interest	1,433	1,467	1,296
Cash paid for income taxes, net of refunds	3,647	2,182	2,470
Changes in Accrued Liabilities Related to Fixed Asset Additions	$ 345	$ 0	$ 0