Stock-Based Compensation

6 Months Ended

Jun. 30, 2020

Share-based Payment Arrangement [Abstract]

Stock-Based Compensation

Stock-Based Compensation

Aggregate stock-based compensation expense was $3.0 million and $5.5 million for the three and six months ended June 30, 2020, compared to $1.8 million and $6.0 million in the three and six months ended June 30, 2019, respectively.

Stock-based compensation expense related to stock options was $0.7 million and $1.3 million for the three and six months ended June 30, 2020, compared to $0.9 million and $1.7 million in the three and six months ended June 30, 2019, respectively.

Expense related to time-based restricted share units was $1.5 million and $2.4 million for the three and six months ended June 30, 2020, compared to $0.4 million and $2.6 million in the three and six months ended June 30, 2019, respectively.

Stock-based compensation expense related to performance-based restricted share units was $0.8 million and $1.7 million for the three and six months ended June 30, 2020, compared to $0.5 million and $1.7 million in the three and six months ended June 30, 2019, respectively.

Expense related to our employee stock purchase plan (“ESPP”) was not material in the three months ended June 30, 2020. ESPP-related expense was $0.1 million for the six months ended June 30, 2020. The ESPP was put in place during 2019 with the first offering period beginning on September 1, 2019 through December 31, 2019. As a result, there was no expense for the ESPP in the three and six months ended June 30, 2019