CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash Flows from Operating Activities:
Net income	$ 193,965	$ 204,289
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	26,511	25,057
Provision for credit losses	2,092	186
Deferred income taxes	(5,028)	5,244
Share-based compensation expense	11,173	8,875
Other	235	333
Changes in assets and liabilities:
Accounts receivable	(37,531)	(54,735)
Inventories	(18,854)	(7,919)
Other assets and liabilities	(52,904)	(57,081)
Accounts payable	(4,016)	2,460
Deferred revenue	(937)	(2,287)
Net cash provided by operating activities	114,706	124,422
Cash Flows from Investing Activities:
Purchases of property and equipment	(31,838)	(20,163)
Acquisition of intangible assets	(10,000)	0
Acquisitions of a business, net of cash acquired	0	(4,424)
Net cash used by investing activities	(41,838)	(24,587)
Cash Flows from Financing Activities:
Borrowings under revolving credit facility, net	326,500	0
Payment of senior debt	(75,000)	0
Repurchases of common stock, net	(266,295)	(132,262)
Proceeds from exercises of stock options and employee stock purchase plans	11,653	17,594
Shares withheld for statutory tax withholding payments on restricted stock	(10,338)	(14,983)
Net cash used by financing activities	(13,480)	(129,651)
Net effect of changes in exchange rates on cash	776	(2,949)
Net increase (decrease) in cash and cash equivalents	60,164	(32,765)
Cash and cash equivalents at beginning of period	144,454	383,928
Cash and cash equivalents at end of period	204,618	351,163
Supplemental Cash Flow Information:
Cash paid for income taxes	11,400	12,171
Unpaid property and equipment, reflected in accounts payable and accrued liabilities	$ 11,016	$ 6,592