Condensed consolidated statements of stockholders' equity (unaudited) - USD ($) $ in Thousands	Total	Common stock	Additional paid-in capital	Accumulated deficit
Beginning balance at Mar. 31, 2019	$ 215,215	$ 483	$ 744,147	$ (529,415)
Beginning balance (in shares) at Mar. 31, 2019		48,288,720,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	3,706			3,706
Stock-based compensation	3,926		3,926
Exercise of stock options and vesting of restricted stock	240	$ 2	238
Exercise of stock options, net (in shares)		179,225,000
Repurchase of common stock	(1,079)	$ (1)	(1,078)
Repurchase of common stock (in shares)		(89,610,000)
Ending balance at Jun. 30, 2019	222,008	$ 484	747,233	(525,709)
Ending balance (in shares) at Jun. 30, 2019		48,378,335,000
Beginning balance at Mar. 31, 2019	215,215	$ 483	744,147	(529,415)
Beginning balance (in shares) at Mar. 31, 2019		48,288,720,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	10,223
Ending balance at Sep. 30, 2019	231,688	$ 485	750,395	(519,192)
Ending balance (in shares) at Sep. 30, 2019		48,526,112,000
Beginning balance at Jun. 30, 2019	222,008	$ 484	747,233	(525,709)
Beginning balance (in shares) at Jun. 30, 2019		48,378,335,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	6,517			6,517
Stock-based compensation	4,004		4,004
Exercise of stock options and vesting of restricted stock	626	$ 2	624
Exercise of stock options, net (in shares)		236,803,000
Repurchase of common stock	(1,467)	$ (1)	(1,466)
Repurchase of common stock (in shares)		(89,026,000)
Ending balance at Sep. 30, 2019	231,688	$ 485	750,395	(519,192)
Ending balance (in shares) at Sep. 30, 2019		48,526,112,000
Beginning balance at Mar. 31, 2020	242,171	$ 489	753,213	(511,531)
Beginning balance (in shares) at Mar. 31, 2020		48,874,742,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,512			1,512
Stock-based compensation	4,627		4,627
Exercise of stock options and vesting of restricted stock	398	$ 2	396
Exercise of stock options, net (in shares)		175,561,000
Ending balance at Jun. 30, 2020	248,708	$ 491	758,236	(510,019)
Ending balance (in shares) at Jun. 30, 2020		49,050,303,000
Beginning balance at Mar. 31, 2020	242,171	$ 489	753,213	(511,531)
Beginning balance (in shares) at Mar. 31, 2020		48,874,742,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,959
Ending balance at Sep. 30, 2020	254,653	$ 494	763,731	(509,572)
Ending balance (in shares) at Sep. 30, 2020		49,314,029,000
Beginning balance at Jun. 30, 2020	248,708	$ 491	758,236	(510,019)
Beginning balance (in shares) at Jun. 30, 2020		49,050,303,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	447			447
Stock-based compensation	5,385		5,385
Exercise of stock options and vesting of restricted stock	113	$ 3	110
Exercise of stock options, net (in shares)		263,726,000
Ending balance at Sep. 30, 2020	$ 254,653	$ 494	$ 763,731	$ (509,572)
Ending balance (in shares) at Sep. 30, 2020		49,314,029,000