Share-Based Compensation - Summary of Share-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Summary of share-based compensation expense
Share-based compensation before income tax benefit	$ 2,411	$ 2,045	$ 4,617	$ 2,762
Income tax benefit	(607)	(515)	(1,165)	(696)
Share-based compensation, net of income tax benefit	1,804	1,530	3,452	2,066
Performance Unit Incentive Plan (“PUP”)
Summary of share-based compensation expense
Share-based compensation before income tax benefit	1,557	1,324	2,980	1,518
Restricted stock
Summary of share-based compensation expense
Share-based compensation before income tax benefit	783	667	1,476	1,170
Restricted stock units
Summary of share-based compensation expense
Share-based compensation before income tax benefit	$ 71	$ 54	$ 161	$ 74