Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-In Capital	Accumulated Earnings	Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock, shares, outstanding (in shares)		49,480
Treasury stock, shares (in shares) at Dec. 31, 2018			(9,145)
Beginning 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	3,284				3,284
Other comprehensive income (loss)	352					352
At the market equity offering, net of costs (in shares)		243
At the market equity offering, net of costs	20,216			20,216
Share-based compensation	8,410			8,410
Issuance of common stock under employee stock plans (in shares)		628
Issuance of common stock under employee stock plans	20,526	$ 0		20,526
Tax payments related to restricted stock units	(1,920)			(1,920)
Treasury stock, shares (in shares) at Mar. 31, 2019			(9,145)
Ending balance at Mar. 31, 2019	$ 730,485	$ 50	$ (185,074)	725,273	200,738	(10,502)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock, shares, outstanding (in shares)		50,351
Common stock, shares, outstanding (in shares)	42,132	51,277
Treasury stock, shares (in shares) at Dec. 31, 2019	(9,145)		(9,145)
Beginning balance at Dec. 31, 2019	$ 845,254	$ 51	$ (185,074)	780,931	258,792	(9,446)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	11,311				11,311
Other comprehensive income (loss)	(4,694)					(4,694)
Share-based compensation	10,659			10,659
Issuance of common stock under employee stock plans (in shares)		474
Issuance of common stock under employee stock plans	17,659	$ 1		17,658
Tax payments related to restricted stock units	$ (1,425)			(1,425)
Treasury stock, shares (in shares) at Mar. 31, 2020	(9,145)		(9,145)
Ending balance at Mar. 31, 2020	$ 878,500	$ 52	$ (185,074)	$ 807,823	$ 269,839	$ (14,140)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock, shares, outstanding (in shares)	42,606	51,751