Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities:
Net income	$ 3,335	$ 21,198
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	11,976	14,104
Amortization of purchased intangibles	2,300	3,093
Amortization of capitalized software development costs for products to be sold	1,017	685
Amortization of debt issuance costs	133	133
Amortization of discounts and premiums on investments, net	372	527
Write-down of excess and obsolete inventories	2,314	4,530
Stock-based compensation expense	11,480	9,232
Excess tax benefits from stock-based compensation expense	(1,225)	(3,120)
(Gain) loss on disposal of property and equipment	(32)	541
Changes in assets and liabilities:
Trade receivables	25,171	304
Inventories	(11,158)	1,856
Deferred taxes	(2,297)	(1,469)
Prepaid expenses and other assets	426	(4,651)
Accounts payable	13,342	(1,120)
Taxes payable	4,307	8,498
Other accrued liabilities and deferred revenue	(8,568)	(23,969)
Net cash provided by operating activities	52,893	30,372
Cash flows from investing activities:
Purchases of property and equipment	(6,772)	(11,748)
Capitalized software development costs for products to be sold	(792)	(606)
Purchases of investments	(63,926)	(50,669)
Proceeds from sales of investments	1,600	5,185
Proceeds from maturities of investments	80,548	42,796
Net cash provided by (used in) investing activities	10,658	(15,042)
Cash flows from financing activities:
Proceeds from issuance of common stock under employee option and stock purchase plans	10,706	12,408
Payments on debt	(1,563)	(1,563)
Purchase and retirement of common stock under share repurchase plan		(39,993)
Purchase and retirement of common stock for tax withholdings on vesting of employee stock-based awards	(9,086)	(10,922)
Excess tax benefits from stock-based compensation expense	1,225	3,120
Net cash provided by (used in) financing activities	1,282	(36,950)
Effect of exchange rate changes on cash and cash equivalents	840
Net increase (decrease) in cash and cash equivalents	65,673	(21,620)
Cash and cash equivalents, beginning of period	435,093	443,132
Cash and cash equivalents, end of period	$ 500,766	$ 421,512