Stock-Based Compensation (Tables)

9 Months Ended

Dec. 31, 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 nine months ended December 31, 2015 and 2014:

	For the Three Months Ended December 31,				For the Nine Months Ended December 31,
		2015		2014		2015		2014
	(in $000's)				(in $000's)
Cost of product revenue	$	216	$	160	$	671	$	517
Research and development		994		840		2,914		2,466
Selling, general and administrative		4,929		3,382		18,146		9,713
	$	6,139	$	4,382	$	21,731	$	12,696

Components of Stock-Based Compensation

The components of stock-based compensation for the three and nine months ended December 31, 2015 and 2014 were as follows:

	For the Three Months Ended December 31,				For the Nine Months Ended December 31,
		2015		2014		2015		2014
	(in $000's)				(in $000's)
Restricted stock units	$	5,133	$	3,640	$	17,482	$	10,394
Stock options		909		666		3,955		2,089
Employee stock purchase plan		97		76		294		213
	$	6,139	$	4,382	$	21,731	$	12,696

Summary of Stock Option Activity

The following table summarizes the stock option activity for the nine months ended December 31, 2015:

						Weighted
				Weighted		Average		Aggregate
				Average		Remaining		Intrinsic
	Options			Exercise		Contractual		Value
	(in thousands)			Price		Term (years)		(in thousands)
Outstanding at beginning of period		2,892		$	14.72		5.18
Granted		164			71.15
Exercised		(721	)		11.42
Cancelled and expired		(2	)		13.81
Outstanding at end of period		2,333		$	19.71		5.35	$	164,775
Exercisable at end of period		1,690		$	13.83		4.27	$	129,224
Options vested and expected to vest at end of period		2,273		$	19.33		5.27	$	161,336

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 three and nine months ended December 31, 2015 and 2014 was as follows:

	For the Three Months Ended December 31,						For the Nine Months Ended December 31,
		2015			2014			2015			2014
Weighted average grant-date fair value	$	34.05		$	15.36		$	28.91		$	9.18
Valuation assumptions:
Risk-free interest rate		1.50	%		1.70	%		1.60	%		1.60	%
Expected option life (years)		4.15			4.17			4.14			4.19
Expected volatility		49.6	%		49.7	%		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 nine months ended December 31, 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		679		$	87.95
Vested		(465	)	$	22.65
Forfeited		(45	)	$	15.44
Restricted stock and restricted stock units at end of period		1,329		$	55.61

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)		2.45
Expected volatility		47.2	%
Estimated grant date fair value (per share)	$	107.10
Target performance (number of shares)		107,660