Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect of a Change in Accounting Principle	Common Stock	Treasury Stock	Additional Paid-In Capital	Accumulated Earnings	Accumulated Earnings Cumulative Effect of a Change in Accounting Principle	Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2018			49,480
Treasury stock (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 (loss)	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)
Ending balance (in shares) at Mar. 31, 2019			50,351
Treasury stock (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)
Beginning balance (in shares) at Dec. 31, 2018			49,480
Treasury stock (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 (loss)	39,243
Other comprehensive income (loss)	(3,547)
Ending balance (in shares) at Sep. 30, 2019			51,050
Treasury stock (in shares) at Sep. 30, 2019				(9,145)
Ending balance at Sep. 30, 2019	807,533		$ 51	$ (185,074)	770,260	236,697		(14,401)
Beginning balance (in shares) at Mar. 31, 2019			50,351
Treasury stock (in shares) at Mar. 31, 2019				(9,145)
Beginning balance at Mar. 31, 2019	730,485		$ 50	$ (185,074)	725,273	200,738		(10,502)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	15,976					15,976
Other comprehensive income (loss)	(1,074)							(1,074)
At the market equity offering, net of costs (in shares)			217
At the market equity offering, net of costs	17,590		$ 0		17,590
Share-based compensation	8,260				8,260
Issuance of common stock under employee stock plans (in shares)			216
Issuance of common stock under employee stock plans	4,807		$ 1		4,806
Tax payments related to restricted stock units	(2,802)				(2,802)
Ending balance (in shares) at Jun. 30, 2019			50,784
Treasury stock (in shares) at Jun. 30, 2019				(9,145)
Ending balance at Jun. 30, 2019	773,242		$ 51	$ (185,074)	753,127	216,714		(11,576)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	19,983					19,983
Other comprehensive income (loss)	(2,825)							(2,825)
Share-based compensation	8,505				8,505
Issuance of common stock under employee stock plans (in shares)			266
Issuance of common stock under employee stock plans	9,696		$ 0		9,696
Tax payments related to restricted stock units	(1,068)				(1,068)
Ending balance (in shares) at Sep. 30, 2019			51,050
Treasury stock (in shares) at Sep. 30, 2019				(9,145)
Ending balance at Sep. 30, 2019	$ 807,533		$ 51	$ (185,074)	770,260	236,697		(14,401)
Beginning balance (in shares) at Dec. 31, 2019	42,132		51,277
Treasury stock (in shares) at Dec. 31, 2019	(9,145)			(9,145)
Beginning balance at Dec. 31, 2019	$ 845,254	$ (264)	$ 51	$ (185,074)	780,931	258,792	$ (264)	(9,446)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	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)
Ending balance (in shares) at Mar. 31, 2020			51,751
Treasury stock (in shares) at Mar. 31, 2020				(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]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Beginning balance (in shares) at Dec. 31, 2019	42,132		51,277
Treasury stock (in shares) at Dec. 31, 2019	(9,145)			(9,145)
Beginning balance at Dec. 31, 2019	$ 845,254	$ (264)	$ 51	$ (185,074)	780,931	258,792	$ (264)	(9,446)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	15,817
Other comprehensive income (loss)	$ (733)
Ending balance (in shares) at Sep. 30, 2020	42,274		52,168
Treasury stock (in shares) at Sep. 30, 2020	(9,894)			(9,894)
Ending balance at Sep. 30, 2020	$ 918,399		$ 52	$ (238,109)	892,290	274,345		(10,179)
Beginning balance (in shares) at Mar. 31, 2020			51,751
Treasury stock (in shares) at Mar. 31, 2020				(9,145)
Beginning balance at Mar. 31, 2020	878,500		$ 52	$ (185,074)	807,823	269,839		(14,140)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(4,299)					(4,299)
Other comprehensive income (loss)	451							451
Share-based compensation	11,351				11,351
Issuance of common stock under employee stock plans (in shares)			151
Issuance of common stock under employee stock plans	3,503		$ 0		3,503
Tax payments related to restricted stock units	(2,045)				(2,045)
Ending balance (in shares) at Jun. 30, 2020			51,902
Treasury stock (in shares) at Jun. 30, 2020				(9,145)
Ending balance at Jun. 30, 2020	887,461		$ 52	$ (185,074)	820,632	265,540		(13,689)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	8,805					8,805
Other comprehensive income (loss)	3,510							3,510
Share-based compensation	11,024				11,024
Issuance of common stock under employee stock plans (in shares)			266
Issuance of common stock under employee stock plans	12,064		$ 0		12,064
Tax payments related to restricted stock units	(631)				(631)
Common stock repurchases (in shares)				(749)
Stock repurchases	(53,035)			$ (53,035)
Equity component of convertible senior note issuance, net of issuance costs	97,830				97,830
Purchase of convertible note hedge	(100,625)				(100,625)
Sale of warrants	51,290				51,290
Tax benefits related to convertible senior notes and convertible note hedge	$ 706				706
Ending balance (in shares) at Sep. 30, 2020	42,274		52,168
Treasury stock (in shares) at Sep. 30, 2020	(9,894)			(9,894)
Ending balance at Sep. 30, 2020	$ 918,399		$ 52	$ (238,109)	$ 892,290	$ 274,345		$ (10,179)