Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income	$ 160,338	$ 180,261	$ 404,169
Adjustments to reconcile net income to net cash (used) provided by operating activities:
Depreciation and amortization	94,554	96,268	80,271
Deferred income taxes	(12,813)	(15,489)	(4,576)
Stock-based compensation	35,472	33,363	28,027
Goodwill impairment	44,589	37,120	0
Impairment of long-lived assets	671	5,350	0
Unrealized losses (gains) on foreign currency transactions	(19,935)	11,004	(2,670)
Other	8,642	3,320	(3,586)
Provisions for inventory, warranty and bad debt	70,572	63,752	38,862
Changes in assets and liabilities that (used) provided cash, net of acquisitions:
Accounts receivable	(13,022)	9,776	(18,814)
Inventories	(39,900)	(28,105)	(135,440)
Prepaid expenses and other current assets	(3,802)	18,405	(7,062)
Accounts payable	(1,942)	(10,257)	(1,426)
Accrued expenses and other liabilities	(14,752)	(37,310)	(19,666)
Income and other taxes payable	(23,337)	(43,937)	35,212
Net cash provided by operating activities	285,335	323,521	393,301
Cash flows from investing activities:
Purchases of property, plant and equipment	(87,696)	(133,536)	(160,343)
Proceeds from sales of property, plant and equipment	889	661	1,026
Proceeds from short-term investments	1,099,224	768,078	470,328
Purchases of short and long-term investments	(1,111,555)	(760,300)	(765,310)
Acquisitions of businesses, net of cash acquired	(429)	(15,115)	(109,115)
Other	(7)	237	415
Net cash used in investing activities	(99,574)	(139,975)	(562,999)
Cash flows from financing activities:
Proceeds from line-of-credit facilities	0	15	255
Payments on line-of-credit facilities	0	(15)	(255)
Principal payments on long-term borrowings	(3,740)	(3,671)	(3,604)
Proceeds from issuance of common stock under employee stock option and purchase plans less payments for taxes related to net share settlement of equity awards	33,194	7,336	12,183
Cash contributed by non-controlling interest	0	0	839
Purchase of treasury stock, at cost	(37,884)	(40,732)	(176,065)
Payment of purchase price holdback from business combination	(1,650)	0	0
Net cash used in financing activities	(10,080)	(37,067)	(166,647)
Effect of changes in exchange rates on cash, cash equivalents and restricted cash	19,888	(7,853)	(29,197)
Net increase (decrease) in cash, cash equivalents and restricted cash	195,569	138,626	(365,542)
Cash, cash equivalents and restricted cash — Beginning of year	682,984	544,358	909,900
Cash, cash equivalents and restricted cash — End of year (Note 1)	878,553	682,984	544,358
Supplemental disclosure of cash flow information:
Cash paid for interest	2,234	2,683	3,052
Cash paid for income taxes	85,861	116,951	112,762
Non-cash transactions:
Demonstration units transferred from inventory to other assets	8,117	10,367	6,270
Property, plant and equipment transferred from inventory	4,243	7,659	2,535
Changes in accounts payable related to property, plant and equipment	(75)	1,304	(2,852)
Leased assets obtained in exchange for new operating lease liabilities	$ 4,035	$ 14,670	$ 0