Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash Flows from Operating Activities
Net income	$ 272,509	$ 249,624	$ 268,550
Adjustments to reconcile net income to net cash provided by operations:
Depreciation and amortization	60,865	59,172	59,051
Stock option expense	30,082	26,254	22,502
Deferred payroll taxes		(18,175)	(18,175)	$ 36,400
Noncash portion of long-term incentive compensation	9,267	6,188	7,745
(Benefit)/provision for deferred income taxes	(8,027)	14,827	2,400
Litigation settlements	2,050	4,000
Litigation settlements			(9,440)
Noncash directors' compensation	1,444	1,170	1,173
Amortization of debt issuance costs	580	342	306
Changes in operating assets and liabilities:
Increase in accounts receivable	(41,488)	(2,414)	(8,431)
Increase in inventories	(1,732)	(162)	(3,014)
Decrease/(increase) in prepaid expenses	87	2,397	(6,511)
(Decrease)/increase in accounts payable and other current liabilities	(9,348)	15,343	9,832
Change in current income taxes	11,748	(996)	(20,401)
Net change in lease assets and liabilities	(1,424)	1,471	(44)
Increase in other assets	(9,952)	(45,779)	(10,305)
Increase/(decrease) in other liabilities	12,802	(3,350)	12,074
Other sources/(uses)	836	(26)	1,285
Net cash provided by operating activities	330,299	309,886	308,597
Cash Flows from Investing Activities
Capital expenditures	(56,854)	(57,325)	(58,675)
Business combinations, net of cash acquired	(3,994)	(3,529)
Proceeds from sale of fixed assets	640	2,330	904
Other (uses)/sources	(434)	(878)	14
Net cash used by investing activities	(60,642)	(59,402)	(57,757)
Cash Flows from Financing Activities
Proceeds from exercise of stock options	102,192	44,968	35,848
Payments on other long-term debt	(97,500)	(2,500)
Proceeds from other long-term debt		100,000
Purchases of treasury stock	(67,697)	(114,515)	(576,042)
Dividends paid	(23,502)	(22,017)	(22,016)
Change in cash overdrafts payable	15,749	(11,884)	11,884
Capital stock surrendered to pay taxes on stock-based compensation	(9,557)	(15,611)	(15,129)
Payments on revolving line of credit		(306,800)	(25,300)
Proceeds from revolving line of credit		121,800	210,300
Debt issuance costs		(1,586)
Other sources/(uses)	490	(1,108)	(165)
Net cash used by financing activities	(79,825)	(209,253)	(380,620)
Increase/(decrease) in cash and cash equivalents	189,832	41,231	(129,780)
Cash and cash equivalents at beginning of year	74,126	32,895	162,675
Cash and cash equivalents at end of year	$ 263,958	$ 74,126	$ 32,895	$ 162,675