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)
Common Stock, Beginning of period (in shares) at Dec. 31, 2015		44,739
Stockholders' Equity, Beginning of period at Dec. 31, 2015	$ 420,464	$ 45	$ (185,074)	$ 490,354	$ 117,869	$ (2,730)
Treasury Stock, Beginning of period (in shares) at Dec. 31, 2015			9,145
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	9,756				9,756
Other comprehensive loss	(6,789)					(6,789)
Share-based compensation	19,500			19,500
Issuance of common stock under employee stock plans (in shares)		1,039
Issuance of common stock under employee stock plans	17,692	$ 1		17,691
Tax payments related to restricted stock units	(3,490)			(3,490)
Income tax benefits from employee stock plans	1,703			1,703
Common Stock, End of period (in shares) at Dec. 31, 2016		45,778
Stockholders' Equity, End of period at Dec. 31, 2016	458,836	$ 46	$ (185,074)	525,758	127,625	(9,519)
Treasury Stock, End of period (in shares) at Dec. 31, 2016			9,145
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	30,518				30,518
Other comprehensive 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
Common Stock, End of period (in shares) at Dec. 31, 2017		47,577
Stockholders' Equity, End of period at Dec. 31, 2017	$ 554,341	$ 48	$ (185,074)	585,755	159,725	(6,113)
Treasury Stock, End of period (in shares) at Dec. 31, 2017	9,145		9,145
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of a change in accounting principle related to share-based compensation	$ 1,582				1,582
Net income	37,729				37,729
Other comprehensive 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)
Common Stock, End of period (in shares) at Dec. 31, 2018		49,480
Stockholders' Equity, End of period at Dec. 31, 2018	$ 679,617	$ 50	$ (185,074)	$ 678,041	$ 197,454	$ (10,854)
Treasury Stock, End of period (in shares) at Dec. 31, 2018	9,145		9,145