Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]
Beginning Balance at Dec. 31, 2019	$ 171,799	$ 75	$ 20,227	$ 2,819	$ 148,678
Beginning Balance, shares at Dec. 31, 2019		7,514
Common stock issued on exercise of options, purchase of ESPP shares and vesting of restricted stock units and performance awards	3,084	$ 2	3,082
Common stock issued on exercise of options, purchase of ESPP shares and vesting of restricted stock units and performance awards, shares		223
Common stock repurchased on vesting of restricted stock units and performance awards	(1,417)		(1,417)
Common stock repurchased on vesting of restricted stock units and performance awards, shares		(27)
Share-based compensation expense	3,436		3,436
Company repurchase of common stock	(8,056)	$ (1)	(443)		(7,612)
Company repurchase of common stock, shares		(144)
Cash dividends on common stock	(9,121)				(9,121)
Unrealized gain (loss) on investments, net of tax	4,745			4,745
Net income	33,765				33,765
Ending Balance at Dec. 31, 2020	198,235	$ 76	24,885	7,564	165,710
Ending Balance, shares at Dec. 31, 2020		7,566
Common stock issued on exercise of options, purchase of ESPP shares and vesting of restricted stock units and performance awards	1,156	$ 1	1,155
Common stock issued on exercise of options, purchase of ESPP shares and vesting of restricted stock units and performance awards, shares		106
Common stock repurchased on vesting of restricted stock units and performance awards	(1,465)		(1,465)
Common stock repurchased on vesting of restricted stock units and performance awards, shares		(20)
Share-based compensation expense	5,366		5,366
Company repurchase of common stock	(17,287)	$ (3)	(887)		(16,397)
Company repurchase of common stock, shares		(237)
Cash dividends on common stock	(9,069)				(9,069)
Unrealized gain (loss) on investments, net of tax	(6,485)			(6,485)
Net income	38,079				38,079
Ending Balance at Dec. 31, 2021	208,530	$ 74	29,054	1,079	178,323
Ending Balance, shares at Dec. 31, 2021		7,415
Common stock issued on exercise of options, purchase of ESPP shares and vesting of restricted stock units and performance awards	711	$ 1	710
Common stock issued on exercise of options, purchase of ESPP shares and vesting of restricted stock units and performance awards, shares		84
Common stock repurchased on vesting of restricted stock units and performance awards	(1,692)		(1,692)
Common stock repurchased on vesting of restricted stock units and performance awards, shares		(22)
Share-based compensation expense	7,390		7,390
Company repurchase of common stock	(47,168)	$ (6)	(2,718)		(44,444)
Company repurchase of common stock, shares		(606)
Cash dividends on common stock	(8,524)				(8,524)
Unrealized gain (loss) on investments, net of tax	(28,673)			(28,673)
Net income	47,268				47,268
Ending Balance at Dec. 31, 2022	$ 177,842	$ 69	$ 32,744	$ (27,594)	$ 172,623
Ending Balance, shares at Dec. 31, 2022		6,871