Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2019

Schedule of Stock Based Compensation Expense

Our stock-based compensation expense was as follows for the three months ended March 31, 2019 and 2018 (in thousands):

	Three Months Ended March 31,
	2019		2018
Restricted stock units	$	3,147	$	1,164
Performance units		2,759		728
Restricted stock issued to directors		95		89
Total expense	$	6,001	$	1,981

Summary of Employee Restricted Stock Unit Awards Activity

A summary of employee restricted stock unit awards activity during the three months ended March 31, 2019 is as follows:

	Number of shares			Weighted average grant date fair value		Aggregate intrinsic value (in thousands)
Total awarded and unvested, December 31, 2018		233,960		$	29.27	$	3,685
Granted		70,409			17.55
Vested		(198,279	)		29.28
Forfeited		(485	)		31.78
Total awarded and unvested, March 31, 2019		105,605		$	21.42	$	1,588

Summary of Performance Stock Unit Awards Activity

A summary of performance stock unit awards activity during the three months ended March 31, 2019 is as follows

	Number of shares			Weighted average grant date fair value		Aggregate intrinsic value (in thousands)
Total awarded and unvested, December 31, 2018		346,589		$	27.68	$	716
Granted		—			—
Vested		(265,311	)		27.54
Forfeited		(16,001	)		24.47
Total awarded and unvested, March 31, 2019		65,277		$	29.02	$	1,201

Performance Units [Member]

Assumptions Used to Determine Fair Value of Performance Stock Units Granted

The following table presents the assumptions used to determine the fair value for performance stock units granted during the three months ended March 31, 2018:

	Three Months Ended March 31,
	2018
Volatility		89.70	%
Risk-free interest rate		2.37	%