CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 231,418	$ 189,682	$ 144,020
Adjustments to reconcile net income to net cash provided by operating activities:
Deferred taxes	17,572	(16,401)	(11,424)
Depreciation and amortization	37,739	24,002	18,004
Stock-based compensation	58,854	54,148	52,943
Net tax benefits from stock-based awards	0	15,888	10,224
Excess tax benefit from share-based payment arrangements	0	(16,773)	(10,396)
Equity in losses of investee	3,219	1,684	0
Other non-cash operating activities	13,847	12,031	13,799
Changes in assets and liabilities, net of effects of acquisitions:
Accounts receivable	(90,990)	(94,444)	(40,775)
Inventories	(5,481)	(7,663)	(3,563)
Prepaid expenses and other assets	(8,669)	(9,390)	(3,726)
Accounts payable	8,175	(3,395)	7,575
Accrued and other long-term liabilities	24,235	30,007	12,532
Long-term income tax payable	68,958	7,622	6,930
Deferred revenues	79,662	60,656	41,854
Net cash provided by operating activities	438,539	247,654	237,997
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisition, net of cash acquired	(8,953)	0	0
Purchase of property, plant and equipment	(195,695)	(70,576)	(53,451)
Purchase of marketable securities	(390,244)	(405,612)	(447,092)
Proceeds from maturities of marketable securities	349,240	387,873	304,125
Purchase of equity method investments	(12,764)	(46,745)	0
Proceeds from sales of marketable securities	39,536	216,119	30,011
Loan advances to equity investee	(36,000)	0	0
Loan repayment from equity investee	6,000	0	0
Other investing activities	567	(8,211)	46
Net cash provided by (used in) investing activities	(248,313)	72,848	(166,361)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock	14,461	13,778	11,325
Common stock repurchases	(103,793)	(96,218)	(101,791)
Excess tax benefit from share-based payment arrangements	0	16,773	10,396
Employees’ taxes paid upon the vesting of restricted stock units	(46,168)	(29,857)	(20,716)
Net cash used in financing activities	(135,500)	(95,524)	(100,786)
Effect of foreign exchange rate changes on cash and cash equivalents	5,510	(3,417)	(3,007)
Net increase (decrease) in cash and cash equivalents	60,236	221,561	(32,157)
Cash and cash equivalents, beginning of year	389,275	167,714	199,871
Cash and cash equivalents, end of year	$ 449,511	$ 389,275	$ 167,714