Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash Flows from Operating Activities
Net income	$ 205,714	$ 154,343
Adjustments to reconcile net income to net cash provided by operating activities:
Ununtilized CARES Act grant	48,041
Depreciation and amortization	42,237	31,110
Deferred payroll taxes	22,941
Stock option expense	13,296	10,729
Noncash long-term incentive compensation	5,301	4,184
Litigation settlement	2,684	6,000
Noncash directors' compensation	1,171	767
Provision/(benefit) for deferred income taxes	831	(6,085)
Amortization of debt issuance costs	229	229
Asset impairment loss		2,266
Changes in operating assets and liabilities:
Decrease in accounts receivable	27,993	10,558
Increase in inventories	(84)	(1,649)
Increase in prepaid expenses	(2,072)	(6,836)
Increase in accounts payable and other current liabilities	34,526	28,622
Change in current income taxes	(4,366)	(81)
Net change in lease assets and liabilities	1,583	1,311
Increase in other assets	(9,646)	(8,145)
Increase in other liabilities	10,735	9,045
Other sources	1,298	1,277
Net cash provided by operating activities	402,412	237,645
Cash Flows from Investing Activities
Capital expenditures	(42,670)	(39,753)
Business combinations	(3,600)	(138,010)
Other sources	672	101
Net cash used by investing activities	(45,598)	(177,662)
Cash Flows from Financing Activities
Payments on revolving line of credit	(264,900)	(359,900)
Proceeds from revolving line of credit	174,900	400,700
Purchases of treasury stock	(147,123)	(71,926)
Proceeds from exercise of stock options	31,498	23,383
Capital stock surrendered to pay taxes on stock-based compensation	(18,707)	(26,108)
Dividends paid	(15,639)	(14,657)
Change in cash overdrafts payable	(9,849)	(7,535)
Other (uses)/sources	(387)	295
Net cash used by financing activities	(250,207)	(55,748)
Increase in Cash and Cash Equivalents	106,607	4,235
Cash and cash equivalents at beginning of year	6,158	4,831
Cash and cash equivalents at end of period	$ 112,765	$ 9,066