Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Retained Earnings [Member]
Beginning Balance at Dec. 31, 2018	$ 119,037	$ 74	$ 15,437	$ (5,068)	$ 108,594
Beginning Balance, shares at Dec. 31, 2018		7,395
Common stock issued on exercise of options, purchase of ESPP shares and vesting of restricted stock units and performance awards	122		122
Common stock issued on exercise of options, purchase of ESPP shares and vesting of restricted stock units and performance awards, shares		17
Common stock repurchased on vesting of restricted stock units and performance awards	(178)		(178)
Common stock repurchased on vesting of restricted stock units and performance awards, shares		(2)
Share-based compensation expense	1,387		1,387
Cash dividends on common stock	(1,852)				(1,852)
Unrealized gain (loss) on investments, net of tax	3,657			3,657
Net loss	(2,300)				(2,300)
Ending Balance at Mar. 31, 2019	119,873	$ 74	16,768	(1,411)	104,442
Ending Balance, shares at Mar. 31, 2019		7,410
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	904	$ 1	903
Common stock issued on exercise of options, purchase of ESPP shares and vesting of restricted stock units and performance awards, shares		56
Common stock repurchased on vesting of restricted stock units and performance awards	(378)		(378)
Common stock repurchased on vesting of restricted stock units and performance awards, shares		(6)
Share-based compensation expense	342		342
Company repurchase of common stock	(2,987)	$ (1)	(169)		(2,817)
Company repurchase of common stock, shares		(59)
Cash dividends on common stock	(2,262)				(2,262)
Unrealized gain (loss) on investments, net of tax	(2,735)			(2,735)
Net loss	(3,407)				(3,407)
Ending Balance at Mar. 31, 2020	$ 161,276	$ 75	$ 20,925	$ 84	$ 140,192
Ending Balance, shares at Mar. 31, 2020		7,505