Share-Based Compensation - Summary of Share-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Summary of share-based compensation expense
Share-based compensation before income tax benefit	$ 2,210	$ 1,025	$ 4,709	$ 3,131
Income tax benefit	(812)	(381)	(1,750)	(1,180)
Share-based compensation, net of income tax benefit	1,398	644	2,959	1,951
Performance unit incentive plan (“PUP”)
Summary of share-based compensation expense
Share-based compensation before income tax benefit	1,601	456	2,952	1,444
Restricted stock
Summary of share-based compensation expense
Share-based compensation before income tax benefit	523	523	1,597	1,623
Restricted stock units
Summary of share-based compensation expense
Share-based compensation before income tax benefit	$ 86	$ 46	$ 160	$ 64