Condensed Consolidated Statements of Changes in Stockholder's Equity - USD ($) $ in Thousands	Total	Common Stock	Additional  Paid-in Capital	Accumulated Other Comprehensive Earnings (Loss)	Retained Earnings
Balance (in shares) at Dec. 31, 2018		52,316,583
Balance at Dec. 31, 2018	$ 453,023	$ 52	$ 369,637	$ (3,158)	$ 86,492
Increase (Decrease) in Stockholders' Equity
Share-based compensation	3,287		3,287
Exercise of stock options (in shares)		57,665
Exercise of stock options	783		783
Net earnings	18,340				18,340
Unrealized (loss) gain on marketable securities, net of tax	4,585			4,585
Balance (in shares) at Mar. 31, 2019		52,374,248
Balance at Mar. 31, 2019	480,018	$ 52	373,707	1,427	104,832
Balance (in shares) at Dec. 31, 2019		52,533,348
Balance at Dec. 31, 2019	595,428	$ 53	388,410	7,417	199,548
Increase (Decrease) in Stockholders' Equity
Share-based compensation	3,988		3,988
Exercise of stock options (in shares)		3,811
Exercise of stock options	32		32
Net earnings	21,518				21,518
Unrealized (loss) gain on marketable securities, net of tax	(7,583)			(7,583)
Balance (in shares) at Mar. 31, 2020		52,537,159
Balance at Mar. 31, 2020	$ 613,383	$ 53	$ 392,430	$ (166)	$ 221,066