Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2019

Stock-based Compensation

Summary of the stock-based compensation activity

	Quarter ended March 31,
	2019		2018
	(in thousands)
Grants:
Units:
Performance-based RSUs		665		524
Stock options		344		674
Time-based RSUs		330		316
Grant date fair value:
Performance-based RSUs	$	15,253	$	12,791
Stock options		2,965		6,147
Time-based RSUs		7,545		7,703
Total	$	25,763	$	26,641
Vestings and exercises:
Performance-based RSUs vested		648		—
Stock options exercised		89		196
Time-based RSUs vested		291		234
Compensation expense	$	4,531	$	6,171