Share-Based Compensation - Summary of Share-Based Compensation Expenses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Summary of share-based compensation expense
Share-based compensation before income tax benefit	$ 1,066	$ 1,231
Income tax benefit	(398)	(462)
Share-based compensation, net of income tax benefit	668	769
Restricted Stock
Summary of share-based compensation expense
Share-based compensation before income tax benefit	498	594
Performance unit incentive plan (“PUP”)
Summary of share-based compensation expense
Share-based compensation before income tax benefit	535	612
Restricted stock units
Summary of share-based compensation expense
Share-based compensation before income tax benefit	$ 33	$ 25