Stock-Based Compensation Plans (Tables)

6 Months Ended

Jun. 30, 2021

Share-based Payment Arrangement, Noncash Expense [Abstract]

Schedule of components of stock compensation expense

The components of stock-based compensation expense were as follows:

	Three months ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
	(in thousands)				(in thousands)
2007 Stock Incentive Plan	$	957	$	703	$	1,642	$	1,728
2018 Stock Incentive Plan	3,507		2,237		5,506		3,297
Employee Stock Purchase Plan	72		75		150		107
Total Stock Compensation Expense	$	4,536	$	3,015	$	7,298	$	5,132

Summary of restricted stock activity

The following table summarizes restricted stock activity under the 2007 and 2018 Plans during the six months ended June 30, 2021:

	Shares
Balance as of December 31, 2020	581,715
Shares granted	286,550
Shares forfeited	—
Shares vested	(339,657)
Balance as of June 30, 2021	528,608