Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2019

Stock-Based Compensation Expense

The following table presents stock-based compensation expense in the Company’s consolidated statements of comprehensive income:

	Three Months Ended March 31,
	2019		2018
	(Amounts in thousands)
Cost of product revenue	$	324	$	266
Research and development		321		170
Selling, general and administrative		2,606		1,832
Total stock-based compensation	$	3,251	$	2,268

Estimated Weighted Average Assumptions

Information regarding option activity for the three months ended March 31, 2019 under the Plans is summarized below:

	Shares			Weighted average exercise price		Weighted- Average Remaining Contractual Term (in Years)		Aggregate Intrinsic Value (in Thousands)
Options outstanding at December 31, 2018		998,226		$	27.54
Granted		31,498		$	59.52
Exercised		(1,893	)	$	22.35
Forfeited/expired/cancelled		—		$	—
Options outstanding at March 31, 2019		1,027,831		$	28.53		7.04	$	31,469
Options exercisable at March 31, 2019		540,600		$	21.66		5.54	$	20,231
Vested and expected to vest at March 31, 2019(1)		985,138					6.96	$	30,511

(1) Represents the number of vested options as of March 31, 2019 plus the number of unvested options expected to vest as of March 31, 2019 based on the unvested outstanding options at March 31, 2019 adjusted for estimated forfeiture rates of 8% for awards granted to non-executive level employees and 3% for awards granted to executive level employees.

Summary of Restricted Stock Unit Activity

Information regarding RSU activity for the three months ended March 31, 2019 under the Plans is summarized below:

	Shares			Weighted- Average Remaining Contractual Term (in Years)		Aggregate Intrinsic Value (in Thousands)
Unvested at December 31, 2018		705,413
Awarded		147,474
Vested		(154,837	)
Forfeited/expired/cancelled		(17,501	)
Unvested at March 31, 2019		680,549			3.88	$	40,207
Vested and expected to vest at March 31, 2019(1)		622,851			3.54	$	36,798

(1) Represents the number of vested RSUs units as of March 31, 2019 plus the number of unvested RSUs expected to vest as of March 31, 2019 based on the unvested outstanding RSUs at March 31, 2019 adjusted for estimated forfeiture rates of 8% for awards granted to non-executive level employees and 3% for awards granted to executive level employees.