Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net income	$ 180,261	$ 404,169	$ 347,588
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	96,268	80,271	64,568
Deferred income taxes	(15,489)	(4,576)	22,881
Stock-based compensation	33,363	28,027	23,021
Goodwill impairment	37,120	0	0
Impairment of long-lived assets	5,350	0	0
Unrealized losses (gains) on foreign currency transactions	11,004	(2,670)	7,949
Other	3,320	(3,586)	986
Provisions for inventory, warranty and bad debt	63,752	38,862	44,978
Changes in assets and liabilities that (used) provided cash, net of acquisitions:
Accounts receivable	9,776	(18,814)	(63,225)
Inventories	(28,105)	(135,440)	(71,080)
Prepaid expenses and other current assets	18,405	(7,062)	(911)
Accounts payable	(10,257)	(1,426)	2,309
Accrued expenses and other liabilities	(37,310)	(19,666)	9,612
Income and other taxes payable	(43,937)	35,212	16,719
Net cash provided by operating activities	323,521	393,301	405,395
Cash flows from investing activities:
Purchases of property, plant and equipment	(133,536)	(160,343)	(126,535)
Proceeds from sales of property, plant and equipment	661	1,026	15,882
Proceeds from short-term investments	768,078	470,328	212,515
Purchases of short and long-term investments	(760,300)	(765,310)	(211,832)
Acquisitions of businesses, net of cash acquired	(15,115)	(109,115)	(60,483)
Other	237	415	(352)
Net cash used in investing activities	(139,975)	(562,999)	(170,805)
Cash flows from financing activities:
Proceeds from line-of-credit facilities	15	255	6,761
Payments on line-of-credit facilities	(15)	(255)	(6,761)
Proceeds on long-term borrowings	0	0	28,000
Principal payments on long-term borrowings	(3,671)	(3,604)	(19,842)
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	7,336	12,183	28,654
Cash contributed by non-controlling interest	0	839	0
Purchase of non-controlling interests	0	0	(197)
Purchase of treasury stock, at cost	(40,732)	(176,065)	(39,987)
Net cash used in financing activities	(37,067)	(166,647)	(3,372)
Effect of changes in exchange rates on cash, cash equivalents and restricted cash	(7,853)	(29,197)	54,827
Net increase (decrease) in cash, cash equivalents and restricted cash	138,626	(365,542)	286,045
Cash and cash equivalents — Beginning of period	544,358	909,900	623,855
Cash, cash equivalents and restricted cash — End of period (Note 1)	682,984	544,358	909,900
Supplemental disclosure of cash flow information:
Cash paid for interest	2,683	3,052	2,583
Cash paid for income taxes	116,951	112,762	155,559
Non-cash transactions:
Demonstration units transferred from inventory to other assets	10,367	6,270	4,114
Property, plant and equipment transferred from inventory	7,659	2,535	8,425
Changes in accounts payable related to property, plant and equipment	1,304	(2,852)	1,594
Leased assets obtained in exchange for new operating lease liabilities	$ 14,670	$ 0	$ 0