Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income, net of taxes	Retained Earnings	Treasury Stock
Beginning balance (in shares) at Dec. 31, 2020		75,798
Beginning balance at Dec. 31, 2020	$ 480,461	$ 758	$ 282,206	$ 5,563	$ 200,893	$ (8,959)
Comprehensive income (loss)
Net income	24,653				24,653
Unrealized gain (loss) on available-for-sale marketable securities, net of taxes	(1,271)			(1,271)
Total comprehensive (loss) income	23,382
Exercise of stock options and other share-based compensation, net of shares tendered for payment (in shares)		156
Exercise of stock options and other share-based compensation, net of shares tendered for payment	1,475	$ 2	1,473
Payment of statutory withholding on issuance of restricted stock units	(1,501)		(1,501)
Share-based compensation expense	2,104		2,104
Treasury shares issued for Deferred Compensation Plan funding and redemptions	509		545			(36)
Shares issued pursuant to Employee Stock Plan	2,052		1,554			498
Dividends paid and accrued	(15,526)				(15,526)
Shares issued pursuant to Dividend Reinvestment Plan	23		18			5
Other (in shares)		4
Other	123		123
Ending balance (in shares) at Mar. 31, 2021		75,958
Ending balance at Mar. 31, 2021	$ 493,102	$ 760	286,522	4,292	210,020	(8,492)
Comprehensive income (loss)
Cash dividend paid per common share (in dollars per share)	$ 0.21
Beginning balance (in shares) at Dec. 31, 2020		75,798
Beginning balance at Dec. 31, 2020	$ 480,461	$ 758	282,206	5,563	200,893	(8,959)
Comprehensive income (loss)
Net income	43,758
Unrealized gain (loss) on available-for-sale marketable securities, net of taxes	(1,582)
Total comprehensive (loss) income	42,176
Ending balance (in shares) at Sep. 30, 2021		75,997
Ending balance at Sep. 30, 2021	480,205	$ 760	291,899	3,981	197,550	(13,985)
Beginning balance (in shares) at Mar. 31, 2021		75,958
Beginning balance at Mar. 31, 2021	493,102	$ 760	286,522	4,292	210,020	(8,492)
Comprehensive income (loss)
Net income	9,565				9,565
Unrealized gain (loss) on available-for-sale marketable securities, net of taxes	703			703
Total comprehensive (loss) income	10,268
Exercise of stock options and other share-based compensation, net of shares tendered for payment (in shares)		11
Exercise of stock options and other share-based compensation, net of shares tendered for payment	380		380
Share-based compensation expense	2,159		2,159
Purchases of Treasury Stock	(1,835)					(1,835)
Treasury shares issued for Deferred Compensation Plan funding and redemptions	(1)		60			(61)
Dividends paid and accrued	(15,792)				(15,792)
Shares issued pursuant to Dividend Reinvestment Plan	23		17			6
Ending balance (in shares) at Jun. 30, 2021		75,969
Ending balance at Jun. 30, 2021	$ 488,304	$ 760	289,138	4,995	203,793	(10,382)
Comprehensive income (loss)
Cash dividend paid per common share (in dollars per share)	$ 0.21
Net income	$ 9,540				9,540
Unrealized gain (loss) on available-for-sale marketable securities, net of taxes	(1,014)			(1,014)
Total comprehensive (loss) income	8,526
Exercise of stock options and other share-based compensation, net of shares tendered for payment (in shares)		28
Exercise of stock options and other share-based compensation, net of shares tendered for payment	383		383
Payment of statutory withholding on issuance of restricted stock units	100		100
Share-based compensation expense	2,214		2,214
Purchases of Treasury Stock	(3,562)					(3,562)
Treasury shares issued for Deferred Compensation Plan funding and redemptions	0		50			(50)
Dividends paid and accrued	(15,783)				(15,783)
Shares issued pursuant to Dividend Reinvestment Plan	23		14			9
Ending balance (in shares) at Sep. 30, 2021		75,997
Ending balance at Sep. 30, 2021	$ 480,205	$ 760	291,899	3,981	197,550	(13,985)
Comprehensive income (loss)
Cash dividend paid per common share (in dollars per share)	$ 0.21
Beginning balance (in shares) at Dec. 31, 2021	73,769	76,009
Beginning balance at Dec. 31, 2021	$ 452,677	$ 760	294,124	4,000	183,957	(30,164)
Comprehensive income (loss)
Net income	11,329				11,329
Unrealized gain (loss) on available-for-sale marketable securities, net of taxes	(5,269)			(5,269)
Total comprehensive (loss) income	6,060
Exercise of stock options and other share-based compensation, net of shares tendered for payment (in shares)		145
Exercise of stock options and other share-based compensation, net of shares tendered for payment	410	$ 2	408
Payment of statutory withholding on issuance of restricted stock units	(1,069)		(1,069)
Share-based compensation expense	2,298		2,298
Treasury shares issued for Deferred Compensation Plan funding and redemptions	524		110			414
Shares issued pursuant to Employee Stock Plan	1,512		368			1,144
Dividends paid and accrued	(15,859)				(15,859)
Shares issued pursuant to Dividend Reinvestment Plan	25		6			19
Other (in shares)		4
Other	59		59
Ending balance (in shares) at Mar. 31, 2022		76,158
Ending balance at Mar. 31, 2022	$ 446,637	$ 762	296,304	(1,269)	179,427	(28,587)
Comprehensive income (loss)
Cash dividend paid per common share (in dollars per share)	$ 0.21
Beginning balance (in shares) at Dec. 31, 2021	73,769	76,009
Beginning balance at Dec. 31, 2021	$ 452,677	$ 760	294,124	4,000	183,957	(30,164)
Comprehensive income (loss)
Net income	18,471
Unrealized gain (loss) on available-for-sale marketable securities, net of taxes	(9,507)
Total comprehensive (loss) income	$ 8,964
Ending balance (in shares) at Sep. 30, 2022	74,088	76,160
Ending balance at Sep. 30, 2022	$ 422,076	$ 762	300,241	(5,507)	154,501	(27,921)
Beginning balance (in shares) at Mar. 31, 2022		76,158
Beginning balance at Mar. 31, 2022	446,637	$ 762	296,304	(1,269)	179,427	(28,587)
Comprehensive income (loss)
Net income	6,820				6,820
Unrealized gain (loss) on available-for-sale marketable securities, net of taxes	(1,945)			(1,945)
Total comprehensive (loss) income	4,875
Exercise of stock options and other share-based compensation, net of shares tendered for payment (in shares)		2
Share-based compensation expense	2,292		2,292
Treasury shares issued for Deferred Compensation Plan funding and redemptions	(5)		(196)			191
Dividends paid and accrued	(15,980)				(15,980)
Shares issued pursuant to Dividend Reinvestment Plan	26		5			21
Ending balance (in shares) at Jun. 30, 2022		76,160
Ending balance at Jun. 30, 2022	$ 437,845	$ 762	298,405	(3,214)	170,267	(28,375)
Comprehensive income (loss)
Cash dividend paid per common share (in dollars per share)	$ 0.21
Net income	$ 322				322
Unrealized gain (loss) on available-for-sale marketable securities, net of taxes	(2,293)			(2,293)
Total comprehensive (loss) income	(1,971)
Payment of statutory withholding on issuance of restricted stock units	(2)		(2)
Share-based compensation expense	2,271		2,271
Treasury shares issued for Deferred Compensation Plan funding and redemptions	(6)		(432)			426
Dividends paid and accrued	(16,088)				(16,088)
Shares issued pursuant to Dividend Reinvestment Plan	$ 27		(1)			28
Ending balance (in shares) at Sep. 30, 2022	74,088	76,160
Ending balance at Sep. 30, 2022	$ 422,076	$ 762	$ 300,241	$ (5,507)	$ 154,501	$ (27,921)
Comprehensive income (loss)
Cash dividend paid per common share (in dollars per share)	$ 0.21