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 income	$ 149,572	$ 187,074	$ 121,485
Adjustments to reconcile net income to net cash provided by operating activities:
(Gain) loss on sale of discontinued business	255	(78,182)	0
Stock-based compensation expense	20,558	20,168	15,158
Depreciation of property, plant, and equipment	11,678	9,868	8,443
Amortization of intangible assets	3,391	4,250	4,024
Amortization of discounts or premiums on investments	383	690	1,823
Realized (gain) loss on sale of investments	(1,506)	(344)	(673)
Revaluation of contingent consideration	(463)	(790)	0
Change in deferred income taxes	(1,908)	(1,409)	(2,364)
Accounts receivable	(13,251)	(3,950)	(915)
Unbilled revenue	(2,308)	(242)	(563)
Inventories	10,409	(9,457)	(11,750)
Accounts payable	2,087	(8,872)	10,896
Accrued expenses	7,771	(2,831)	7,812
Accrued income taxes	2,110	9,957	7,700
Deferred revenue and customer deposits	(3,188)	1,527	5,893
Other	(3,509)	870	(3,128)
Net cash provided by operating activities	182,081	128,327	163,841
Cash flows from investing activities:
Purchases of investments	(751,868)	(686,650)	(422,633)
Maturities and sales of investments	657,250	601,441	339,470
Purchases of property, plant, and equipment	(12,816)	(18,228)	(20,934)
Cash paid for acquisition of business, net of cash acquired	(14,285)	(1,023)	0
Cash paid for purchased technology	0	(10,475)	0
Net cash received (paid) from sale of discontinued business	(113)	104,388	0
Net cash used in investing activities	(121,832)	(10,547)	(104,097)
Cash flows from financing activities:
Issuance of common stock under stock plans	43,468	27,582	16,930
Repurchase of common stock	(47,149)	(126,351)	(59,673)
Payment of dividends	(25,213)	(18,062)	0
Payment of contingent consideration	(337)	0	0
Net cash used in financing activities	(29,231)	(116,831)	(42,743)
Effect of foreign exchange rate changes on cash and cash equivalents	(3,352)	(4,668)	(1,951)
Net change in cash and cash equivalents	27,666	(3,719)	15,050
Cash and cash equivalents at beginning of year	51,975	55,694	40,644
Cash and cash equivalents at end of year	79,641	51,975	55,694
Stock-based compensation expense	0	1,533	1,099
Depreciation and amortization expense	0	566	1,141
Capital expenditures	$ 0	$ 482	$ 631