STOCKHOLDERS' EQUITY (Tables)

12 Months Ended

Mar. 31, 2020

Equity [Abstract]

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs

The following table summarizes stock-based compensation expense (in thousands):

	Years Ended March 31,
	2020		2019		2018
Cost of service revenue	$	5,330	$	3,752	$	2,636
Cost of other revenue	3,051		1,775		1,341
Research and development	19,712		12,313		6,625
Sales and marketing	20,205		11,951		6,630
General and administrative	22,580		14,717		11,944
Total	$	70,878	$	44,508	$	29,176

Disclosure Of Share-Based Compensation Arrangements By Share-Based Payment Award

Stock option activities under all the Company's stock option plans during the years ended March 31, 2020, 2019 and 2018 are summarized as follows:

	Number of Shares		Weighted Average Exercise Price Per Share
Outstanding at March 31, 2017	4,462,412		7.52
Granted	609,135		14.95
Exercised	(773,897	)	3.95
Canceled/Forfeited	(299,365	)	13.05
Outstanding at March 31, 2018	3,998,285		8.93
Granted	236,799		21.65
Exercised	(759,884	)	7.70
Canceled/Forfeited	(361,129	)	15.41
Outstanding at March 31, 2019	3,114,071		9.45
Granted	—		—
Exercised	(785,281	)	8.77
Canceled/Forfeited	(54,527	)	17.01
Outstanding at March 31, 2020	2,274,263		9.50
Vested and expected to vest March 31, 2020	2,255,616		9.42
Exercisable at March 31, 2020	2,115,696

Stock purchase right activities during the years ended March 31, 2020, 2019 and 2018 are summarized as follows:

	Number of Shares		Weighted Average Grant Date Fair Value		Weighted Average Remaining Contractual Term (in Years)
Balance at March 31, 2017	11,370		$	8.10	1.09
Granted	—		—
Vested and released	(6,395	)	8.26
Forfeited	—		—
Balance at March 31, 2018	4,975		8.10		1.09
Granted	—		—
Vested and released	(4,625	)	7.88
Forfeited	(350	)	7.88
Balance at March 31, 2019 and 2020	—		—		0.00

Activities related to PSUs and RSUs during the years ended March 31, 2020, 2019 and 2018 are summarized as follows:

	Number of Shares		Weighted Average Grant Date Fair Value		Weighted Average Remaining Contractual Term (in Years)
Balance at March 31, 2017	4,939,050		$	11.57	1.55
Granted	3,481,870		14.41
Vested and released	(1,833,038	)	10.27
Forfeited	(652,339	)	12.73
Balance at March 31, 2018	5,935,543		13.51		1.60
Granted	5,726,787		19.77
Vested and released	(2,399,371	)	12.87
Forfeited	(1,442,471	)	16.85
Balance at March 31, 2019	7,820,488		17.68		1.35
Granted	6,431,505		20.62
Vested and released	(3,443,335	)	17.02
Forfeited	(1,617,343	)	19.06
Balance at March 31, 2020	9,191,315				1.89

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions

The fair value of each of the Company's option grants has been estimated on the date of grant using the Black-Scholes pricing model with the following assumptions:

	Years Ended March 31,
	2020	2019	2018
Expected volatility	—%	41%	41%
Expected dividend yield	—	—	—
Risk-free interest rate	0	2.5% to 3.0%	1.8% to 2.4%
Weighted average expected term (in years)	N/A	4.5 years	4.8 years
Weighted average fair value of options granted	$—	$8.19	$5.70

Schedule of Share-based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions

The estimated fair value of stock purchase rights granted under the Employee Stock Purchase Plan was estimated using the Black-Scholes pricing model with the following weighted-average assumptions:

	Years Ended March 31,
	2020	2019	2018
Expected volatility	32%	41%	40%
Expected dividend yield	—	—	—
Risk-free interest rate	1.79%	2.43%	1.33%
Weighted average expected term (in years)	0.7 years	0.8 years	0.8 years
Weighted average fair value of rights granted	$5.66	$5.74	$4.10