Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities:
Net Income	$ 6,651	$ 5,014
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	4,323	3,347
Amortization of net premium on available-for-sale investments	124	220
Net realized gain on long-term investments	(470)	(1,728)
Net (gain) loss on disposal of property, plant and equipment	(16)	3
Stock-based compensation expense	1,883	1,558
Deferred income taxes	(1,947)	435
Changes in operating assets and liabilities:
Accounts receivable, net	7,247	4,752
Other receivables	1,884	10,200
Inventory	(7,399)	163
Prepaid expenses and other assets	(2,413)	(3,083)
Accounts payable	(1,713)	(6,520)
Accrued expenses and other liabilities	(3,166)	902
Income tax payable/receivable, net	4,049	413
Net cash provided by operating activities	9,037	15,676
Cash flows from investing activities:
Purchases of property, plant and equipment	(3,872)	(3,166)
Proceeds from disposals of property, plant and equipment	16
Proceeds from sales and maturities of available-for-sale investments	24,471	60,586
Purchases of available-for-sale investments	(29,517)	(52,053)
Net cash provided by (used in) investing activities	(8,902)	5,367
Cash flows from financing activities:
Proceeds from stock option exercises	1,377	247
Purchases of treasury stock	(5,559)	(11,003)
Dividend payments	(4,369)	(4,453)
Net cash used in financing activities	(8,551)	(15,209)
Net increase (decrease) in cash and cash equivalents	(8,416)	5,834
Effect of exchange rate changes	1,079	1,225
Cash and cash equivalents, beginning of period	79,895	84,550
Cash and cash equivalents, end of period	72,558	91,609
Supplemental disclosure of non-cash investing activities:
Purchases of property, plant and equipment included in accounts payable	$ 509	$ 485