Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Statement of Cash Flows [Abstract]
Net income	$ 122,872	$ 90,305
Adjustments to reconcile net income to net cash provided by operating activities:
Loss/(gain) on sale of assets and other	118	(147)
Depreciation and amortization	22,753	19,739
Noncash lease expense	4,914	4,025
Loss in equity method investment, before tax	2,653	0
Deferred income taxes	1,144	1,973
Noncash compensation related to stock plans	10,245	5,428
Provision of doubtful accounts	(377)	(35)
Changes in operating assets and liabilities:
Trade accounts receivable	(84,702)	(95,875)
Inventories	(27,270)	(14,377)
Trade accounts payable	10,774	15,268
Other current assets	(14,802)	(4,529)
Accrued liabilities and other current liabilities	35,879	22,923
Other noncurrent assets and liabilities	(2,569)	(1,932)
Net cash provided by operating activities	81,632	42,766
Cash flows from investing activities
Capital expenditures	(19,296)	(14,083)
Asset acquisitions, net of cash acquired	(218)	0
Equity method investments	(6,829)	0
Proceeds from sale of property and equipment	129	639
Net cash used in investing activities	(26,214)	(13,444)
Cash flows from financing activities
Repurchase of common stock	0	(62,679)
Proceeds from lines of credit	0	159,412
Repayments of lines of credit and capital leases	(384)	(10,387)
Debt issuance costs	0	(712)
Dividends paid	(19,956)	(20,158)
Cash paid on behalf of employees for shares withheld	(5,263)	(7,743)
Net cash provided by (used in) financing activities	(25,603)	57,733
Effect of exchange rate changes on cash and cash equivalents	1,342	(1,817)
Net increase in cash and cash equivalents	31,157	85,238
Cash and cash equivalents at beginning of period	274,639	230,210
Cash and cash equivalents at end of period	305,796	315,448
Noncash activity during the period
Noncash capital expenditures	1,462	1,308
Dividends declared but not paid	10,847	9,989
Issuance of Company’s common stock for compensation	$ 692	$ 322