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
Issuance of common stock in connection with the Company’s equity award plans (in shares)		57,665
Issuance of common stock in connection with the Company’s equity award plans	783		783
Net earnings	18,340				18,340
Unrealized gain (loss) 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, 2018		52,316,583
Balance at Dec. 31, 2018	453,023	$ 52	369,637	(3,158)	86,492
Increase (Decrease) in Stockholders' Equity
Net earnings	79,927
Unrealized gain (loss) on marketable securities, net of tax	10,419
Balance (in shares) at Sep. 30, 2019		52,462,936
Balance at Sep. 30, 2019	557,257	$ 52	383,525	7,261	166,419
Balance (in shares) at Mar. 31, 2019		52,374,248
Balance at Mar. 31, 2019	480,018	$ 52	373,707	1,427	104,832
Increase (Decrease) in Stockholders' Equity
Share-based compensation	4,022		4,022
Issuance of common stock in connection with the Company’s equity award plans (in shares)		74,788
Issuance of common stock in connection with the Company’s equity award plans	1,640		1,640
Net earnings	32,727				32,727
Unrealized gain (loss) on marketable securities, net of tax	4,497			4,497
Balance (in shares) at Jun. 30, 2019		52,449,036
Balance at Jun. 30, 2019	522,904	$ 52	379,369	5,924	137,559
Increase (Decrease) in Stockholders' Equity
Share-based compensation	3,914		3,914
Issuance of common stock in connection with the Company’s equity award plans (in shares)		13,900
Issuance of common stock in connection with the Company’s equity award plans	242		242
Net earnings	28,860				28,860
Unrealized gain (loss) on marketable securities, net of tax	1,337			1,337
Balance (in shares) at Sep. 30, 2019		52,462,936
Balance at Sep. 30, 2019	557,257	$ 52	383,525	7,261	166,419
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
Issuance of common stock in connection with the Company’s equity award plans (in shares)		3,811
Issuance of common stock in connection with the Company’s equity award plans	32		32
Net earnings	21,518				21,518
Unrealized gain (loss) 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
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
Net earnings	96,182
Unrealized gain (loss) on marketable securities, net of tax	2,283
Balance (in shares) at Sep. 30, 2020		52,670,121
Balance at Sep. 30, 2020	708,879	$ 53	403,396	9,700	295,730
Balance (in shares) at Mar. 31, 2020		52,537,159
Balance at Mar. 31, 2020	613,383	$ 53	392,430	(166)	221,066
Increase (Decrease) in Stockholders' Equity
Share-based compensation	4,962		4,962
Issuance of common stock in connection with the Company’s equity award plans (in shares)		86,925
Issuance of common stock in connection with the Company’s equity award plans	1,437		1,437
Net earnings	34,667				34,667
Unrealized gain (loss) on marketable securities, net of tax	11,525			11,525
Balance (in shares) at Jun. 30, 2020		52,624,084
Balance at Jun. 30, 2020	665,974	$ 53	398,829	11,359	255,733
Increase (Decrease) in Stockholders' Equity
Share-based compensation	4,490		4,490
Issuance of common stock in connection with the Company’s equity award plans (in shares)		46,037
Issuance of common stock in connection with the Company’s equity award plans	77		77
Net earnings	39,997				39,997
Unrealized gain (loss) on marketable securities, net of tax	(1,659)			(1,659)
Balance (in shares) at Sep. 30, 2020		52,670,121
Balance at Sep. 30, 2020	$ 708,879	$ 53	$ 403,396	$ 9,700	$ 295,730