Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities:
Net income	$ 43,758	$ 70,935
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	10,961	10,752
Bad debt provision	10,790	6,756
Deferred income tax expense (benefit)	198	(8,247)
Share-based compensation expense	6,968	5,917
Amortization of premium on marketable securities	1,740	1,409
Unrealized gain on deferred compensation fund investments	(3,958)	(4,210)
Loss on sale of assets	1,157	0
Changes in operating assets and liabilities:
Accounts and notes receivable	(41,275)	22,440
Inventories and supplies	4,872	3,825
Prepaid expenses and other assets	(23,459)	(3,588)
Deferred compensation funding	72	488
Accounts payable and other accrued expenses	10,694	(9,104)
Accrued payroll, accrued and withheld payroll taxes	(26,085)	14,356
Income taxes payable	0	17,420
Accrued insurance claims	4,871	8,450
Deferred compensation liability	4,427	3,950
Net cash provided by operating activities	5,731	141,549
Cash flows from investing activities:
Disposals of fixed assets	201	475
Additions to property and equipment	(4,202)	(3,074)
Purchases of marketable securities	(16,683)	(8,242)
Sales of marketable securities	12,368	5,979
Cash paid for acquisition	(6,000)	0
Net cash used in investing activities	(14,316)	(4,862)
Cash flows from financing activities:
Dividends paid	(46,672)	(45,383)
Reissuance of treasury stock pursuant to Dividend Reinvestment Plan	69	69
Proceeds from the exercise of stock options	2,238	1,893
Purchases of treasury stock	(5,397)	0
Repayments of short-term borrowings	0	(10,000)
Payments of statutory withholding on net issuance of restricted stock units	(1,401)	(675)
Net cash used in financing activities	(51,163)	(54,096)
Net change in cash and cash equivalents	(59,748)	82,591
Cash and cash equivalents at beginning of the period	139,330	27,329
Cash and cash equivalents at end of the period	79,582	109,920
Supplemental disclosure of non-cash investing activities
Accrued variable consideration from acquisition of a business	$ 10,562	$ 0