CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash Flows from Operating Activities:
Net income	$ 111,856	$ 102,709
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	23,204	21,355
Provision for credit losses	4,229	365
Benefit of deferred income taxes	2,853	3,294
Share-based compensation expense	7,284	6,334
Other	(13)	263
Changes in assets and liabilities:
Accounts receivable	(38,062)	(33,421)
Inventories	(14,434)	(14,521)
Other assets and liabilities	(64,881)	(49,601)
Accounts payable	(1,755)	699
Deferred revenue	(2,410)	(3,098)
Net cash provided by operating activities	27,871	34,378
Cash Flows from Investing Activities:
Purchases of property and equipment	(49,002)	(38,206)
Acquisitions of intangible assets	(668)	0
Net cash used by investing activities	(49,670)	(38,206)
Cash Flows from Financing Activities:
Borrowing (repayments) on revolving credit facilities, net	198,110	(52,024)
Issuance of senior notes	0	100,000
Debt issuance costs	0	(30)
Payment of acquisition-related contingent consideration	0	(573)
Repurchases of common stock, net	(182,815)	(54,302)
Proceeds from exercises of stock options and employee stock purchase plans	10,210	11,551
Shares withheld for statutory tax withholding on restricted stock	(8,604)	(7,403)
Net cash provided (used) by financing activities	16,901	(2,781)
Net effect of changes in exchange rates on cash	(4,033)	(569)
Net decrease in cash and cash equivalents	(8,931)	(7,178)
Cash and cash equivalents at beginning of period	90,326	123,794
Cash and cash equivalents at end of period	81,395	116,616
Supplemental Cash Flow Information:
Cash paid for income taxes	12,020	8,717
Unpaid property and equipment, reflected in accounts payable and accrued liabilities	$ 14,123	$ 9,007