Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands		Total		Adjustment to adopt credit-loss guidance, net of tax	[1]	Adoption, adjusted balance	[1]	Common Stock	Common Stock Adoption, adjusted balance	Additional Paid-in Capital	Additional Paid-in Capital Adoption, adjusted balance	Accumulated Other Comprehensive Income (Loss), net of Taxes	Accumulated Other Comprehensive Income (Loss), net of Taxes Adoption, adjusted balance	Retained Earnings	Retained Earnings Adjustment to adopt credit-loss guidance, net of tax	[1]	Retained Earnings Adoption, adjusted balance	Treasury Stock	Treasury Stock Adoption, adjusted balance
Balance (in shares) at Dec. 31, 2019								75,557	75,557
Beginning balance at Dec. 31, 2019		$ 460,305	[1]	$ (32,099)		$ 428,206		$ 756	$ 756	$ 270,614	$ 270,614	$ 2,919	$ 2,919	$ 195,455	$ (32,099)		$ 163,356	$ (9,439)	$ (9,439)
Comprehensive income:
Net income for the period		98,682	[1]											98,682
Unrealized gain (loss) on available-for-sale marketable securities, net of taxes		2,644	[1]									2,644
Total comprehensive income	[1]	101,326
Exercise of stock options and other stock-based compensation, net of shares tendered for payment (in shares)								235
Exercise of stock options and other share-based compensation, net of shares tendered for payment		2,920	[1]					$ 2		2,918
Payment of statutory withholding on issuance of restricted stock units		(675)	[1]							(675)
Share-based expense		7,329	[1]							7,329
Treasury shares issued for Deferred Compensation Plan funding		385	[1]							438								(53)
Shares issued pursuant to Employee Stock Plan		1,835	[1]							1,329								506
Dividends paid and accrued		(61,145)	[1]											(61,145)
Shares issued pursuant to Dividend Reinvestment Plan		93	[1]							66								27
Other (in shares)								6
Other		187	[1]							187
Balance (in shares) at Dec. 31, 2020								75,798
Ending balance at Dec. 31, 2020		480,461	[1]					$ 758		282,206		5,563		200,893				(8,959)
Comprehensive income:
Net income for the period		45,863	[1]											45,863
Unrealized gain (loss) on available-for-sale marketable securities, net of taxes		(1,563)	[1]									(1,563)
Total comprehensive income	[1]	44,300
Exercise of stock options and other stock-based compensation, net of shares tendered for payment (in shares)								207
Exercise of stock options and other share-based compensation, net of shares tendered for payment		2,425	[1]					$ 2		2,423
Payment of statutory withholding on issuance of restricted stock units		(1,410)	[1]							(1,410)
Share-based expense		8,600	[1]							8,600
Purchases of treasury stock		(21,535)	[1]															(21,535)
Treasury shares issued for Deferred Compensation Plan funding		368	[1]							574								(206)
Shares issued pursuant to Employee Stock Plan		2,052	[1]							1,554								498
Dividends paid and accrued		(62,799)	[1]											(62,799)
Shares issued pursuant to Dividend Reinvestment Plan		92	[1]							54								38
Other (in shares)								4
Other		$ 123	[1]							123
Balance (in shares) at Dec. 31, 2021		73,769						76,009
Ending balance at Dec. 31, 2021		$ 452,677	[1]					$ 760		294,124		4,000		183,957				(30,164)
Comprehensive income:
Net income for the period		34,630	[1]											34,630
Unrealized gain (loss) on available-for-sale marketable securities, net of taxes		(7,477)	[1]									(7,477)
Total comprehensive income	[1]	27,153
Exercise of stock options and other stock-based compensation, net of shares tendered for payment (in shares)								148
Exercise of stock options and other share-based compensation, net of shares tendered for payment		410	[1]					$ 2		408
Payment of statutory withholding on issuance of restricted stock units		(1,071)	[1]							(1,071)
Share-based expense		9,044	[1]							9,044
Purchases of treasury stock		0
Treasury shares issued for Deferred Compensation Plan funding		374	[1]							(634)								1,008
Shares issued pursuant to Employee Stock Plan		1,512	[1]							368								1,144
Dividends paid and accrued		(64,092)	[1]											(64,092)
Shares issued pursuant to Dividend Reinvestment Plan		106	[1]							6								100
Other (in shares)								4
Other		$ 59	[1]							59
Balance (in shares) at Dec. 31, 2022		74,088						76,161
Ending balance at Dec. 31, 2022		$ 426,172	[1]					$ 762		$ 302,304		$ (3,477)		$ 154,495				$ (27,912)

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