Share-Based Compensation - Summary of Share-Based Compensation Expenses (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Summary of share-based compensation expense
Share-based compensation before income tax benefit	$ 391	$ 1,819
Income tax benefit	(152)	(654)
Total share-based compensation, net of income tax benefit	239	1,165
Restricted stock/performance-based restricted stock (PBRS)
Summary of share-based compensation expense
Share-based compensation before income tax benefit	654	773
Performance unit incentive plan (PUP)
Summary of share-based compensation expense
Share-based compensation before income tax benefit	(231)	863
Restricted Stock Units and Performance Based Restricted Stock Units
Summary of share-based compensation expense
Share-based compensation before income tax benefit	(32)	88
Stock options
Summary of share-based compensation expense
Share-based compensation before income tax benefit	$ 0	$ 95