Stock Award Plans and Stock-Based Compensation (Tables)

12 Months Ended

Mar. 31, 2018

Stock-Based Compensation Recognized

The following table summarizes stock-based compensation expense by financial statement line item in the Company’s consolidated statements of operations for the fiscal years ended March 31, 2018, 2017 and 2016:

	Fiscal Years Ended March 31,
		2018		2017		2016
	(in $000's)
Cost of revenue	$	1,721	$	1,061	$	895
Research and development		5,895		6,050		3,950
Selling, general and administrative		32,737		25,755		24,208
	$	40,353	$	32,866	$	29,053

Components of Stock-Based Compensation

The components of stock-based compensation for the fiscal years ended March 31, 2018, 2017 and 2016 were as follows:

	Fiscal Years Ended March 31,
		2018		2017		2016
	(in $000's)
Restricted stock units	$	34,559	$	26,570	$	23,708
Stock options		5,202		5,829		4,866
Employee stock purchase plan		592		467		479
	$	40,353	$	32,866	$	29,053

Summary of Stock Option Activity

The following table summarized stock option activity for the fiscal year ended March 31, 2018:

						Weighted
				Weighted		Average		Aggregate
				Average		Remaining		Intrinsic
	Options			Exercise		Contractual		Value
	(in thousands)			Price		Term (years)		(in thousands)
Outstanding at beginning of period		1,646		$	32.09		5.46
Granted		155			143.52
Exercised		(460	)		20.23
Cancelled and expired		(59	)		98.21
Outstanding at end of period		1,282		$	46.81		5.31	$	313,158
Exercisable at end of period		965		$	24.88		4.29	$	256,891
Options vested and expected to vest at end of period		1,259		$	46.18		5.27	$	308,252

Summary of Weighted Average Grant-Date Fair Values And Weighted Average Assumptions Used to Calculate Fair Value of Options Granted

The weighted average grant-date fair values and weighted average assumptions used in the calculation of fair value of options granted during the fiscal years ended March 31, 2018, 2017 and 2016 was as follows:

	Fiscal Years Ended March 31,
		2018			2017			2016
Valuation assumptions:
Weighted average grant-date fair value	$	52.34		$	42.40		$	29.57
Risk-free interest rate		1.87	%		1.41	%		1.55	%
Expected option life (years)		4.07			4.14			4.15
Expected volatility		43.5	%		48.9	%		49.7	%

Summary of Restricted Stock Units Activity

The following table summarizes restricted stock unit activity for the fiscal year ended March 31, 2018:

	Number of Shares			Weighted Average Grant Date Fair Value
	(in thousands)			(per share)
Restricted stock units at beginning of period		1,056		$	80.50
Granted		296		$	137.40
Vested		(372	)	$	53.40
Forfeited		(100	)	$	98.47
Restricted stock units at end of period		880		$	109.01

Restricted Stock Units

Monte Carlo Simulation Model to Estimate Grant-Date Fair Value of Restricted Stock Units

The table below sets forth the assumptions used to value the market-based awards and the estimated grant-date fair value:

	June 2015 Awards				November 2016 Awards
Risk-free interest rate			1.10	%			0.90	%
Dividend yield			0	%			0	%
Remaining performance period (years)			0.21				0.21
Expected volatility			47.2	%			50.6	%
Estimated grant date fair value (per share)	$	93.49 - 107.10			$	62.55
Target performance (number of shares)			107,660				41,526