STOCK-BASED COMPENSATION (Tables)

3 Months Ended

Mar. 31, 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 March 31,
	2018				2017
	Grants		Weighted Average Grant Date Fair Value		Grants		Weighted Average Grant Date Fair Value
Stock options		1,124,585	$	34.08		877,492	$	16.30
Restricted stock units		150,725	$	71.45		161,029	$	32.63
Restricted stock awards		17,090	$	71.45		6,500	$	31.06

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 March 31,
	2018		2017
	(in thousands)
Research and development	$	2,060	$	1,874
Selling, general and administrative		8,466		3,838
Total stock-based compensation expense	$	10,526	$	5,712

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 March 31,
	2018		2017
	(in thousands)
Stock options	$	8,973	$	5,038
Restricted stock awards/units		1,260		204
Employee stock purchase plan ("ESPP")		293		470
Total stock-based compensation expense	$	10,526	$	5,712