Income Taxes--Component of Income Tax Expense (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Current tax expense
Federal tax benefit	$ (29)	$ (23)	$ (21)
State tax expense	1,144	141	200
Current tax expense	1,115	118	179
Deferred tax expense
Federal tax expense	30,327	35,579	27,290
State tax expense	1,407	2,140	8,455
Deferred tax expense	31,734	37,719	35,745
Income tax expense	$ 32,849	$ 37,837	$ 35,924