Consolidated Statements of Shareholders' Equity - USD ($)	Common Stock [Member]	Additional Paid-in Capital Common Stock [Member]	Retained Earnings (Accumulated Deficit) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Beginning balance at Mar. 31, 2014	$ 151,000	$ 120,553,000	$ (10,191,000)	$ (877,000)	$ 109,636,000
Balance (in shares) at Mar. 31, 2014	15,067,645
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Compensation recognized under employee stock plans	$ 0	2,210,000	0	0	2,210,000
Exercise of stock options	$ 1,000	1,246,000			1,247,000
Exercise of stock options (in shares)	123,734
Issuance of common stock upon vesting of RSUs, net of shares withheld for employee taxes	$ 0	(806,000)			(806,000)
Issuance of common stock upon vesting of RSUs, net of shares withheld for employee taxes (in shares)	23,219
Tax benefit from employee stock options exercised	$ 0	1,131,000	0	0	1,131,000
Common stock issued in connection with public offering	$ 28,000	71,732,000	0	0	71,760,000
Common stock issued in connection with public offering (in shares)	2,760,000
Stock issuance costs	$ 0	(4,787,000)			(4,787,000)
Unrealized gain (loss) on investments, net of tax	0	0	0	24,000	24,000
Foreign currency translation	0	0	0	(1,665,000)	(1,665,000)
Net income	0	0	11,453,000	0	11,453,000
Ending balance at Mar. 31, 2015	$ 180,000	191,279,000	1,262,000	(2,518,000)	190,203,000
Balance (in shares) at Mar. 31, 2015	17,974,598
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Compensation recognized under employee stock plans	$ 0	2,584,000	0	0	2,584,000
Exercise of stock options	$ 5,000	5,387,000	0	0	5,392,000
Exercise of stock options (in shares)	510,637
Issuance of common stock upon vesting of RSUs, net of shares withheld for employee taxes	$ 0	(913,000)	0	0	(913,000)
Issuance of common stock upon vesting of RSUs, net of shares withheld for employee taxes (in shares)	46,516
Tax benefit from employee stock options exercised	$ 0	5,313,000	0	0	5,313,000
Unrealized gain (loss) on investments, net of tax	0	0	0	(13,000)	(13,000)
Foreign currency translation	0	0	0	(2,321,000)	(2,321,000)
Net income	0	0	10,563,000	0	10,563,000
Ending balance (As Previously Reported [Member]) at Mar. 31, 2016	$ 185,000	203,650,000	11,825,000	(4,852,000)	210,808,000
Ending balance at Mar. 31, 2016				(4,852,000)	$ 210,808,000
Balance (in shares) (As Previously Reported [Member]) at Mar. 31, 2016	18,531,751
Balance (in shares) at Mar. 31, 2016	18,531,751				18,531,751
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative-effect adjustment (Note 2) | Adjustment [Member] | ASU 2016-09 [Member]	$ 0	0	892,000	0	$ 892,000
Balance April 1, 2016 | ASU 2016-09 [Member]	185,000	203,650,000	12,717,000	(4,852,000)	211,700,000
Compensation recognized under employee stock plans	0	3,383,000	0	0	3,383,000
Exercise of stock options	$ 1,000	1,661,000	0	0	1,662,000
Exercise of stock options (in shares)	133,731
Issuance of common stock upon vesting of RSUs, net of shares withheld for employee taxes	$ 1,000	(1,059,000)	0	0	(1,058,000)
Issuance of common stock upon vesting of RSUs, net of shares withheld for employee taxes (in shares)	53,031
Repurchase and cancellation of treasury stock, including fees	$ (1,000)	(1,989,000)	0	0	(1,990,000)
Repurchase and cancellation of treasury stock, including fees (in shares)	(69,659)
Unrealized gain (loss) on investments, net of tax	$ 0	0	0	196,000	196,000
Foreign currency translation	0	0	0	(2,785,000)	(2,785,000)
Net income	0	0	37,573,000	0	37,573,000
Ending balance at Mar. 31, 2017	$ 186,000	$ 205,646,000	$ 50,290,000	$ (7,441,000)	$ 248,681,000
Balance (in shares) at Mar. 31, 2017	18,648,854				18,648,854