Share-Based Compensation - Summary of Share-Based Compensation Expenses (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Summary of share-based compensation expense
Share-based compensation before income tax benefit	$ 5,221	$ 7,232	$ 4,413
Income tax benefit	(1,936)	(2,574)	(1,594)
Total share-based compensation, net of income tax benefit	3,285	4,658	2,819
Restricted stock/performance-based restricted stock (PBRS)
Summary of share-based compensation expense
Share-based compensation before income tax benefit	3,073	3,267	3,042
Performance unit incentive plan (PUP)
Summary of share-based compensation expense
Share-based compensation before income tax benefit	1,864	2,922	714
Restricted Stock Units and Performance Based Restricted Stock Units
Summary of share-based compensation expense
Share-based compensation before income tax benefit	177	450	120
Stock options
Summary of share-based compensation expense
Share-based compensation before income tax benefit	$ 107	$ 593	$ 537