Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Statement of Cash Flows [Abstract]
Net income	$ 157,362	$ 105,925
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on sale of assets and other	(204)	(263)
Depreciation and amortization	30,088	29,044
Noncash lease expense	6,246	5,278
Deferred income taxes and other long-term liabilities	1,852	2,262
Noncash compensation related to stock plans	9,459	8,699
Provision of doubtful accounts	23	435
Changes in operating assets and liabilities:
Trade accounts receivable	(87,170)	(36,385)
Inventories	(7,199)	31,163
Trade accounts payable	7,825	8,130
Other current assets	(618)	(3,197)
Accrued liabilities and other current liabilities	21,762	3,452
Other noncurrent assets and liabilities	(9,808)	(5,308)
Net cash provided by operating activities	129,618	149,235
Cash flows from investing activities
Capital expenditures	(20,879)	(24,495)
Asset acquisitions, net of cash acquired	(1,425)	(3,529)
Proceeds from sale of property and equipment	750	2,498
Net cash used in investing activities	(21,554)	(25,526)
Cash flows from financing activities
Repurchase of common stock	(62,679)	(51,437)
Proceeds from lines of credit	164,330	13,308
Repayments of lines of credit and capital leases	(89,347)	(14,335)
Payments of Debt Issuance Costs	(712)	0
Dividends paid	(30,164)	(30,002)
Cash paid on behalf of employees for shares withheld	(7,581)	(5,905)
Net cash used by in financing activities	(26,153)	(88,371)
Effect of exchange rate changes on cash and cash equivalents	(656)	(1,457)
Net increase in cash and cash equivalents	81,255	33,881
Cash and cash equivalents at beginning of period	230,210	160,180
Cash and cash equivalents at end of period	311,465	194,061
Noncash activity during the period
Noncash capital expenditures	778	194
Dividends declared but not paid	10,000	10,162
Issuance of Company’s common stock for compensation	$ 342	$ 292