CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash Flows from Operating Activities:
Net income	$ 744,844	$ 582,131	$ 427,792
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	104,596	95,998	88,011
Impairment charge	5,148	2,501	968
Provision for uncollectible accounts	1,484	4,946	662
Deferred income taxes	(3,377)	(38,082)	6,162
Share-based compensation expense	37,755	30,951	39,278
Other	2,619	1,379	1,254
Changes in assets and liabilities:
Accounts receivable	(33,141)	(60,722)	(22,472)
Inventories	(52,919)	(18,885)	(37,306)
Accounts payable	11,233	981	1,957
Deferred revenue	(7,551)	(13,373)	(12,360)
Other assets and liabilities	(55,145)	60,238	(34,788)
Net cash provided by operating activities	755,546	648,063	459,158
Cash Flows from Investing Activities:
Purchases of property and equipment	(119,549)	(106,958)	(154,969)
Acquisitions of intangible assets and equity investments	0	(918)	(255)
Acquisitions of businesses, net of cash acquired	(173,418)	(1,500)	(50,304)
Net cash used by investing activities	(292,967)	(109,376)	(205,528)
Cash Flows from Financing Activities:
Borrowings (repayments) on revolving credit facilities, net	73,500	(289,625)	(110,275)
Issuance of senior notes	0	200,000	100,000
Payments of senior notes	(50,000)	0	0
Debt issuance costs	(2,650)	(5,025)	(154)
Purchase of minority interest	(990)	0	0
Repurchases of common stock, net	(746,777)	(182,815)	(301,658)
Proceeds from exercises of stock options and employee stock purchase plans	46,565	51,328	36,106
Payment of acquisition-related contingent consideration and holdbacks	(1,500)	(1,676)	(2,375)
Shares withheld for statutory tax withholding payments on restricted stock	(15,562)	(20,603)	(8,053)
Net cash used by financing activities	(697,414)	(248,416)	(286,409)
Net effect of changes in exchange rates on cash	(4,639)	3,331	(689)
Net (decrease) increase in cash and cash equivalents	(239,474)	293,602	(33,468)
Cash and cash equivalents at beginning of period	383,928	90,326	123,794
Cash and cash equivalents at end of period	$ 144,454	$ 383,928	$ 90,326