Condensed Consolidated Statement of Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Balance at Mar. 31, 2019	$ 375,946	$ 648	$ 264,908	$ 111,621	$ (1,231)
Balance, Shares at Mar. 31, 2019		64,838
Common stock issued under stock plans, net of shares withheld for taxes	(1,305)	$ 6	(1,311)
Common stock issued under stock plans, net of shares withheld for taxes, Shares		545
Stock-based compensation	4,891		4,891
Other comprehensive income:
Translation adjustments	54				54
Net income (loss)	1,244			1,244
Balance at Jun. 30, 2019	380,830	$ 654	268,488	112,865	(1,177)
Balance, Shares at Jun. 30, 2019		65,383
Balance at Mar. 31, 2019	375,946	$ 648	264,908	111,621	(1,231)
Balance, Shares at Mar. 31, 2019		64,838
Other comprehensive income:
Translation adjustments	(192)
Net income (loss)	11,740
Balance at Dec. 31, 2019	399,756	$ 657	277,161	123,361	(1,423)
Balance, Shares at Dec. 31, 2019		65,701
Balance at Jun. 30, 2019	380,830	$ 654	268,488	112,865	(1,177)
Balance, Shares at Jun. 30, 2019		65,383
Common stock issued under stock plans, net of shares withheld for taxes	44		44
Common stock issued under stock plans, net of shares withheld for taxes, Shares		53
Stock-based compensation	4,316		4,316
Other comprehensive income:
Translation adjustments	(143)				(143)
Net income (loss)	6,081			6,081
Balance at Sep. 30, 2019	391,128	$ 654	272,848	118,946	(1,320)
Balance, Shares at Sep. 30, 2019		65,436
Common stock issued under stock plans, net of shares withheld for taxes	(305)	$ 3	(308)
Common stock issued under stock plans, net of shares withheld for taxes, Shares		265
Stock-based compensation	4,621		4,621
Other comprehensive income:
Translation adjustments	(103)				(103)
Net income (loss)	4,415			4,415
Balance at Dec. 31, 2019	399,756	$ 657	277,161	123,361	(1,423)
Balance, Shares at Dec. 31, 2019		65,701
Balance at Mar. 31, 2020	400,494	$ 661	282,857	119,119	(2,143)
Balance, Shares at Mar. 31, 2020		66,134
Common stock issued under stock plans, net of shares withheld for taxes	(1,408)	$ 6	(1,414)
Common stock issued under stock plans, net of shares withheld for taxes, Shares		535
Stock-based compensation	5,393		5,393
Other comprehensive income:
Translation adjustments	(13)				(13)
Net income (loss)	(824)			(824)
Balance at Jun. 30, 2020	403,642	$ 667	286,836	118,295	(2,156)
Balance, Shares at Jun. 30, 2020		66,669
Balance at Mar. 31, 2020	400,494	$ 661	282,857	119,119	(2,143)
Balance, Shares at Mar. 31, 2020		66,134
Other comprehensive income:
Translation adjustments	260
Net income (loss)	10,095
Balance at Dec. 31, 2020	425,712	$ 670	297,711	129,214	(1,883)
Balance, Shares at Dec. 31, 2020		67,002
Balance at Jun. 30, 2020	403,642	$ 667	286,836	118,295	(2,156)
Balance, Shares at Jun. 30, 2020		66,669
Common stock issued under stock plans, net of shares withheld for taxes	(45)		(45)
Common stock issued under stock plans, net of shares withheld for taxes, Shares		65
Stock-based compensation	5,437		5,437
Other comprehensive income:
Translation adjustments	102				102
Net income (loss)	10,455			10,455
Balance at Sep. 30, 2020	419,591	$ 667	292,228	128,750	(2,054)
Balance, Shares at Sep. 30, 2020		66,734
Common stock issued under stock plans, net of shares withheld for taxes	(447)	$ 3	(450)
Common stock issued under stock plans, net of shares withheld for taxes, Shares		268
Stock-based compensation	5,933		5,933
Other comprehensive income:
Translation adjustments	171				171
Net income (loss)	464			464
Balance at Dec. 31, 2020	$ 425,712	$ 670	$ 297,711	$ 129,214	$ (1,883)
Balance, Shares at Dec. 31, 2020		67,002