STOCK-BASED COMPENSATION (Tables)

6 Months Ended

Jun. 30, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Stock Awards Granted

The following table summarizes the Company’s stock awards granted for each of the periods indicated:

	For the Three Months Ended June 30,								For the Six Months Ended June 30,
	2018				2017				2018				2017
	Grants		Weighted Average Grant Date Fair Value		Grants		Weighted Average Grant Date Fair Value		Grants		Weighted Average Grant Date Fair Value		Grants		Weighted Average Grant Date Fair Value
Stock options		528,096	$	45.45		3,579,467	$	13.64		1,652,681	$	37.71		4,456,959	$	14.16
Restricted stock units		18,695	$	95.38		20,000	$	36.26		169,420	$	74.09		181,029	$	33.03
Restricted stock awards		—	$	—		335,000	$	34.65		17,090	$	71.45		341,500	$	34.58

Summary of Stock-Based Compensation Expense by Function Included within Condensed Consolidated Statements of Operations and Comprehensive Loss

The following table summarizes stock-based compensation expense by function included within the unaudited condensed consolidated statements of operations and comprehensive loss:

	For the Three Months Ended June 30,				For the Six Months Ended June 30,
	2018		2017		2018		2017
	(in thousands)
Research and development	$	5,029	$	2,195	$	7,089	$	4,069
Selling, general and administrative		10,250		8,270		18,716		12,108
Total stock-based compensation expense	$	15,279	$	10,465	$	25,805	$	16,177

Summary of Stock-Based Compensation Expense by Grant Type Included within Condensed Consolidated Statements of Operations and Comprehensive Loss

The following table summarizes stock-based compensation expense by grant type included within the unaudited condensed consolidated statements of operations and comprehensive loss:

	For the Three Months Ended June 30,				For the Six Months Ended June 30,
	2018		2017		2018		2017
	(in thousands)
Stock options	$	9,382	$	6,763	$	18,355	$	11,801
Restricted stock awards/units		5,407		3,250		6,667		3,454
Employee stock purchase plan		490		452		783		922
Total stock-based compensation expense	$	15,279	$	10,465	$	25,805	$	16,177