Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash Flows from Operating Activities
Net income	$ 65,400	$ 55,891
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	14,225	13,865
Payments on previously accrued litigation settlements	(8,490)
Stock option expense	6,106	5,045
Noncash long-term incentive compensation	1,642	1,598
Provision/(benefit) for deferred income taxes	(930)	2,290
Amortization of debt issuance costs	76	76
Provision for bad debts		594
Changes in operating assets and liabilities:
Decrease in accounts receivable	22,773	6,269
Decrease in inventories	318	149
Decrease in prepaid expenses	4,402	1,211
Decrease in accounts payable and other current liabilities	(18,369)	(7,037)
Change in current income taxes	18,395	10,159
Net change in lease assets and liabilities	(24)	(153)
Decrease/(increase) in other assets	(5,274)	5,048
Increase/(decrease) in other liabilities	5,759	(6,067)
Other sources	710	388
Net cash provided by operating activities	106,719	89,326
Cash Flows from Investing Activities
Capital expenditures	(17,697)	(19,897)
Business combinations		(1,452)
Other sources/(uses)	274	(144)
Net cash used by investing activities	(17,423)	(21,493)
Cash Flows from Financing Activities
Purchases of treasury stock	(41,107)	(100,235)
Proceeds from exercise of stock options	11,026	9,241
Capital stock surrendered to pay taxes on stock-based compensation	(6,613)	(7,951)
Dividends paid	(5,437)	(5,130)
Payments on revolving line of credit		(104,100)
Proceeds from revolving line of credit		174,100
Change in cash overdrafts payable		(9,849)
Other sources/(uses)	316	(1,116)
Net cash used by financing activities	(41,815)	(45,040)
Increase in Cash and Cash Equivalents	47,481	22,793
Cash and cash equivalents at beginning of year	162,675	6,158
Cash and cash equivalents at end of period	$ 210,156	$ 28,951