Share-Based Compensation - Summary of Share-Based Compensation Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Summary of share-based compensation expense
Share-based compensation before income tax benefit	$ 1,433	$ 875	$ 2,499	$ 2,106
Income tax benefit	(540)	(325)	(938)	(792)
Share-based compensation, net of income tax benefit	893	550	1,561	1,314
Restricted stock
Summary of share-based compensation expense
Share-based compensation before income tax benefit	576	506	1,074	1,100
Performance unit incentive plan (“PUP”)
Summary of share-based compensation expense
Share-based compensation before income tax benefit	816	376	1,351	988
Restricted stock units
Summary of share-based compensation expense
Share-based compensation before income tax benefit	$ 41	$ (7)	$ 74	$ 18