Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities:
Net Income	$ 19,052	$ 15,242
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	8,377	6,689
Amortization of net premium on available-for-sale investments	238	376
Net realized gain on long-term investments	(1,860)	(2,838)
Net (gain) loss on disposal of property, plant and equipment	(11)	5
Stock-based compensation expense	3,739	3,109
Deferred income taxes	(2,772)	(354)
Changes in operating assets and liabilities:
Accounts receivable, net	13,911	(17,192)
Other receivables	571	7,876
Inventory	(7,547)	4,938
Prepaid expenses and other assets	(9,853)	(4,263)
Accounts payable	(10,910)	10,354
Accrued expenses and other liabilities	(2,629)	1,474
Income tax payable/receivable, net	10,273	(4,799)
Net cash provided by operating activities	20,579	20,617
Cash flows from investing activities:
Purchases of property, plant and equipment	(7,509)	(6,679)
Proceeds from disposals of property, plant and equipment	16
Proceeds from sales and maturities of available-for-sale investments	81,891	109,993
Purchases of available-for-sale investments	(65,140)	(112,903)
Net cash provided by (used in) investing activities	9,258	(9,589)
Cash flows from financing activities:
Proceeds from stock option exercises	1,722	541
Purchases of treasury stock	(17,311)	(16,579)
Dividend payments	(8,719)	(8,860)
Net cash used in financing activities	(24,308)	(24,898)
Net increase (decrease) in cash and cash equivalents	5,529	(13,870)
Effect of exchange rate changes	3,374	234
Cash and cash equivalents, beginning of period	79,895	84,550
Cash and cash equivalents, end of period	88,798	70,914
Supplemental disclosure of non-cash investing activities:
Purchases of property, plant and equipment included in accounts payable	$ 454	$ 554