Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Stock Based Compensation Expense

Our stock-based compensation expense was as follows for the three and nine months ended September 30, 2018 and 2017 (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Restricted stock units	$	1,026	$	1,351	$	3,164	$	3,943
Performance units		1,047		987		2,685		2,627
Restricted stock issued to directors		98		90		282		287
Total expense	$	2,171	$	2,428	$	6,131	$	6,857

Summary of Employee Restricted Stock Unit Awards Activity

A summary of employee restricted stock unit awards activity during the nine months ended September 30, 2018 is as follows:

	Number of shares			Weighted average grant date fair value		Aggregate intrinsic value (in thousands)
Total awarded and unvested, December 31, 2017		4,057,354		$	2.48	$	9,738
Granted		1,498,524			1.70
Vested		(1,986,104	)		2.83
Forfeited		(38,077	)		2.11
Total awarded and unvested, September 30, 2018		3,531,697		$	1.95	$	4,203

Summary of Performance Stock Unit Awards Activity

A summary of performance stock unit awards activity during the nine months ended September 30, 2018 is as follows

	Number of shares			Weighted average grant date fair value		Aggregate intrinsic value (in thousands)
Total awarded and unvested, December 31, 2017		3,966,377		$	1.82	$	11,257
Granted		1,498,524			1.92
Vested		(173,041	)		1.83
Forfeited		(60,127	)		1.83
Total awarded and unvested, September 30, 2018		5,231,733		$	1.85	$	—

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 nine months ended September 30, 2018 and 2017:

	Nine Months Ended September 30,
	2018			2017
Volatility		89.70	%		50.41	%
Risk-free interest rate		2.37	%		1.34	%