Stock-Based Compensation (Tables)

6 Months Ended

Sep. 30, 2015

Stock-Based Compensation Recognized

The following table summarizes stock-based compensation expense by financial statement line item in the Company’s condensed consolidated statements of operations for the three and six months ended September 30, 2015 and 2014:

	For the Three Months Ended September 30,				For the Six Months Ended September 30,
	2015		2014		2015		2014
	(in $000’s)				(in $000’s)
Cost of product revenue	$	218	$	148	$	455	$	357
Research and development		989		773		1,920		1,626
Selling, general and administrative		9,586		3,103		13,217		6,331
	$	10,793	$	4,024	$	15,592	$	8,314

Components of Stock-Based Compensation

The components of stock-based compensation for the three and six months ended September 30, 2015 and 2014 were as follows:

	For the Three Months Ended September 30,				For the Six Months Ended September 30,
	2015		2014		2015		2014
	(in $000’s)				(in $000’s)
Restricted stock units	$	8,446	$	3,334	$	12,349	$	6,754
Stock options		2,227		624		3,046		1,423
Employee stock purchase plan		120		66		197		137
	$	10,793	$	4,024	$	15,592	$	8,314

Summary of Stock Option Activity

The following table summarizes the stock option activity for the six months ended September 30, 2015:

	Options (in thousands)			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (years)		Aggregate Intrinsic Value (in thousands)
Outstanding at beginning of period		2,892		$	14.72		5.18
Granted		145			69.50
Exercised		(703	)		11.33
Cancelled and expired		(1	)		14.00
Outstanding at end of period		2,333		$	19.16		5.56	$	172,712
Exercisable at end of period		1,696		$	13.76		4.50	$	134,674
Options vested and expected to vest at end of period		2,277		$	18.98		5.50	$	169,000

Weighted-Average Assumptions Used to Calculate Fair Value of Options Granted

The fair value of options granted during the three and six months ended September 30, 2015 and 2014 were calculated using the following weighted average assumptions:

	For the Three Months Ended September 30,						For the Six Months Ended September 30,
	2015			2014			2015			2014
Risk-free interest rate		1.63	%		1.75	%		1.59	%		1.60	%
Expected option life (years)		4.13			4.19			4.14			4.19
Expected volatility		48.3	%		48.7	%		49.7	%		49.3	%

Time Based Restricted Stock and Restricted Stock Units

Summary of Restricted Stock and Restricted Stock Units Activity

The following table summarizes the activity of restricted stock and restricted stock units for the six months ended September 30, 2015:

	Number of Shares			Weighted Average Grant Date Fair Value
	(in thousands)			(per share)
Restricted stock and restricted stock units at beginning of period		1,160		$	21.90
Granted		655		$	80.70
Vested		(461	)	$	22.55
Forfeited		(42	)	$	13.09
Restricted stock and restricted stock units at end of period		1,312		$	51.31

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 awards and the estimated grant-date fair value:

Risk-free interest rate		1.10	%
Dividend yield		0	%
Remaining performance period (years)		2.96
Expected volatility		47.2	%
Estimated grant date fair value (per share)	$	107.10
Target performance (number of shares)		107,660