Income Taxes--Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Line Items]
Statutory rate	35.00%	35.00%	35.00%
State income taxes, net of federal benefit	3.80%	2.10%	3.60%
Statutory depletion	(0.70%)	(0.04%)	(0.50%)
Valuation allowance	(1.70%)	0.00%	7.30%
Other	0.70%	(0.04%)	0.70%
Effective tax rate	37.10%	37.00%	46.10%