Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities:
Net income	[1]	$ 34,630	$ 45,863	$ 98,682
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Depreciation and amortization		15,316	14,667	14,268
Bad debt provision		31,969	10,483	9,636
Deferred income tax expense (benefit)		5,049	3,074	(5,893)
Share-based compensation expense		9,214	8,827	7,872
Amortization of premium on marketable securities		2,219	2,275	1,822
Unrealized loss (gain) on deferred compensation fund investments		9,422	(6,397)	(9,390)
Changes in fair value of other long-term liabilities		(2,353)	0	0
Loss on sale of assets		1,138	1,469	1,335
Changes in operating assets and liabilities:
Accounts and notes receivable		(78,707)	(37,185)	46,158
Inventories and supplies		4,851	5,599	4,931
Prepaid expenses and other assets		9,935	(12,250)	(756)
Deferred compensation funding		3,913	6,661	(52)
Accounts payable and other accrued expenses		(13,748)	10,244	(7,250)
Accrued payroll, accrued and withheld payroll taxes		(24,388)	(22,189)	59,527
Income taxes receivable / payable		2,184	(8,420)	(8,075)
Accrued insurance claims		(687)	6,966	(5,194)
Deferred compensation liability		(18,124)	7,421	9,592
Net cash (used in) provided by operating activities		(8,167)	37,108	217,213
Cash flows from investing activities:
Disposals of fixed assets		393	211	274
Additions to property and equipment		(5,210)	(5,687)	(4,341)
Purchases of marketable securities		(2,875)	(20,335)	(39,047)
Sales of marketable securities		10,386	26,697	6,269
Cash paid for acquisitions		(114)	(23,876)	0
Net cash provided by (used in) investing activities		2,580	(22,990)	(36,845)
Cash flows from financing activities:
Dividends paid		(63,373)	(62,226)	(60,705)
Reissuance of treasury stock pursuant to Dividend Reinvestment Plan		106	92	93
Proceeds from the exercise of stock options		410	2,425	2,920
Purchases of treasury stock		0	(21,535)	0
Short-term borrowings, net of repayments		25,000	0	(10,000)
Payments of statutory withholding on net issuance of restricted stock units		(1,071)	(1,410)	(675)
Net cash used in financing activities		(38,928)	(82,654)	(68,367)
Net change in cash and cash equivalents		(44,515)	(68,536)	112,001
Cash and cash equivalents at beginning of the period		70,794	139,330	27,329
Cash and cash equivalents at end of the period		26,279	70,794	139,330
Supplementary cash flow information:
Cash paid for interest		2,822	1,385	1,374
Cash paid for income taxes		3,309	21,233	44,865
Accrued variable consideration for acquisition of businesses		$ 0	$ 10,456	$ 0

[1] See Note 8 — Allowance for Doubtful Accounts herein regarding the adopted credit-loss guidance.