Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-In Capital	Accumulated Earnings	Accumulated Other Comprehensive Income (Loss)
Balance (in shares) at Dec. 31, 2016		45,778
Balance (in shares) at Dec. 31, 2016			(9,145)
Balance at Dec. 31, 2016	$ 458,836	$ 46	$ (185,074)	$ 525,758	$ 127,625	$ (9,519)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	30,518				30,518
Other comprehensive income (loss)	3,406					3,406
At the market offering, net of offering costs (in shares)		294
At the market equity offering, net of costs	13,900			13,900
Share-based compensation	21,857			21,857
Issuance of common stock under employee stock plans (in shares)		1,505
Issuance of common stock under employee stock plans	30,123	$ 2		30,121
Tax payments related to restricted stock units	(5,892)			(5,892)
Income tax benefits from employee stock plans	11			11
Balance (in shares) at Dec. 31, 2017		47,577
Balance (in shares) at Dec. 31, 2017			(9,145)
Balance at Dec. 31, 2017	554,341	$ 48	$ (185,074)	585,755	159,725	(6,113)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	37,729				37,729
Other comprehensive income (loss)	(4,741)					(4,741)
At the market offering, net of offering costs (in shares)		557
At the market equity offering, net of costs	39,567	$ 1		39,566
Share-based compensation	28,885			28,885
Issuance of common stock under employee stock plans (in shares)		1,346
Issuance of common stock under employee stock plans	30,611	$ 1		30,610
Tax payments related to restricted stock units	$ (6,775)			(6,775)
Balance (in shares) at Dec. 31, 2018	40,335	49,480
Balance (in shares) at Dec. 31, 2018	(9,145)		(9,145)
Balance at Dec. 31, 2018	$ 679,617	$ 50	$ (185,074)	678,041	197,454	(10,854)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	61,338				61,338
Other comprehensive income (loss)	1,408					1,408
At the market offering, net of offering costs (in shares)		460
At the market equity offering, net of costs	37,806	$ 0		37,806
Share-based compensation	34,049			34,049
Issuance of common stock under employee stock plans (in shares)		1,337
Issuance of common stock under employee stock plans	40,706	$ 1		40,705
Tax payments related to restricted stock units	$ (9,670)			(9,670)
Balance (in shares) at Dec. 31, 2019	42,132	51,277
Balance (in shares) at Dec. 31, 2019	(9,145)		(9,145)
Balance at Dec. 31, 2019	$ 845,254	$ 51	$ (185,074)	$ 780,931	$ 258,792	$ (9,446)