STOCKHOLDERS' EQUITY AND COMPENSATION ARRANGEMENTS (Tables)

9 Months Ended

Sep. 30, 2020

Share-based Payment Arrangement [Abstract]

Share-based Payment Arrangement, Activity

The stock-based compensation expense related to stock awards issued under the Plans are presented within the following line items of the condensed consolidated statements of operations for the three and nine months ended September 30, 2020 and 2019 (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Cost of revenue	$	156	$	405	$	496	$	1,163
Marketing	377		1,671		1,218		4,586
Selling, general and administrative	7,846		17,467		29,223		56,768
Restructuring and related charges	311		—		1,735		—
Total stock-based compensation expense	$	8,690	$	19,543	$	32,672	$	62,517

We capitalized $1.1 million and $2.0 million of stock-based compensation for the three months ended September 30, 2020 and 2019, and $3.4 million and $5.5 million for the nine months ended September 30, 2020 and 2019 in connection with internally-developed software and cloud computing arrangements.

Schedule of Restricted Stock Unit Activity

The table below summarizes restricted stock unit activity under the Plans for the nine months ended September 30, 2020:

	Restricted Stock Units	Weighted-Average Grant Date Fair Value (per unit)
Unvested at December 31, 2019	1,527,014	$	74.80
Granted	1,744,782	24.59
Vested	(596,183)	74.86
Forfeited	(720,949)	65.70
Unvested at September 30, 2020	1,954,664	33.41

Schedule of Performance and Market-based Performance Share Unit Activity

The table below summarizes Performance Share Unit activity under the Plans for the nine months ended September 30, 2020:

	Performance Share Units	Weighted-Average Grant Date Fair Value (per unit)		Market-based Performance Share Units	Weighted-Average Grant Date Fair Value (per unit)
Unvested at December 31, 2019	203,853	$	79.76	341,002	$	60.60
Granted	96,598	15.44		—	—
Vested	(104,441)	80.77		—	—
Forfeited	(71,128)	79.94		(91,668)	60.60
Unvested at September 30, 2020	124,882	29.78		249,334	60.60
Maximum shares issuable upon vesting at September 30, 2020	173,181			249,334