Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Earnings (Loss)	Retained Earnings (Accumulated Deficit)
Balance (in shares) at Dec. 31, 2016		49,971,267
Balance at Dec. 31, 2016	$ 191,755	$ 50	$ 276,127	$ (134)	$ (84,288)
Increase (Decrease) in Stockholders' Equity
Share-based compensation	8,433		8,433
Issuance of employee stock purchase plan shares (in shares)		71,256
Issuance of employee stock purchase plan shares	1,888		1,888
Exercise of stock options (in shares)		407,477
Exercise of stock options	3,793		3,793
Equity issued on conversion of convertible notes (in shares)		864,850
Equity issued on conversion of convertible notes	4,548	$ 1	4,547
Net earnings	57,284				57,284
Unrealized gain (loss) on marketable securities, net of tax	(613)			(613)
Balance (in shares) at Dec. 31, 2017		51,314,850
Balance at Dec. 31, 2017	267,480	$ 51	294,999	(747)	(26,823)
Increase (Decrease) in Stockholders' Equity
Share-based compensation	11,291		11,291
Issuance of employee stock purchase plan shares (in shares)		71,250
Issuance of employee stock purchase plan shares	2,209		2,209
Exercise of stock options (in shares)		930,483
Exercise of stock options	9,373	$ 1	9,372
Equity issued on conversion of convertible notes	56,215		56,215
Purchase of convertible note hedges, net of tax	(70,137)		(70,137)
Issuance of warrants	65,688		65,688
Net earnings	110,993				110,993
Unrealized gain (loss) on marketable securities, net of tax	(2,411)			(2,411)
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	14,846		14,846
Issuance of employee stock purchase plan shares (in shares)		102,012
Issuance of employee stock purchase plan shares	2,448	$ 1	2,447
Exercise of stock options (in shares)		114,753
Exercise of stock options	1,480		1,480
Net earnings	113,056				113,056
Unrealized gain (loss) on marketable securities, net of tax	10,575			10,575
Balance (in shares) at Dec. 31, 2019		52,533,348
Balance at Dec. 31, 2019	$ 595,428	$ 53	$ 388,410	$ 7,417	$ 199,548