Income Taxes	3 Months Ended
Mar. 31, 2013
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The effective income tax rate for the three months ended March 31, 2013 and 2012 was 39.0% and 37.8%, respectively. The Company's provision for income taxes differed from the U.S. statutory rate of 35% primarily due to state income taxes, domestic production activities deduction, percentage depletion, nondeductible employee compensation and other permanent differences. As of March 31, 2013, the Company had a gross liability for uncertain income tax benefits of $22.6 million, $17.5 million of which, if recognized, would impact the effective income tax rate. There have been no significant changes to the calculation of uncertain income tax benefits during 2013. Consistent with the Company's policy, interest and penalties on income taxes have been recorded as a component of the income tax provision. The Company estimates that it is reasonably possible that the balance of unrecognized income tax benefits as of March 31, 2013 could decrease by a maximum of $6.7 million in the next 12 months due to the expiration of statutes of limitation and audit settlements.

Income Taxes

3 Months Ended

Mar. 31, 2013

The effective income tax rate for the three months ended March 31, 2013 and 2012 was 39.0% and 37.8%, respectively. The Company's provision for income taxes differed from the U.S. statutory rate of 35% primarily due to state income taxes, domestic production activities deduction, percentage depletion, nondeductible employee compensation and other permanent differences.

As of March 31, 2013, the Company had a gross liability for uncertain income tax benefits of $22.6 million, $17.5 million of which, if recognized, would impact the effective income tax rate. There have been no significant changes to the calculation of uncertain income tax benefits during 2013. Consistent with the Company's policy, interest and penalties on income taxes have been recorded as a component of the income tax provision. The Company estimates that it is reasonably possible that the balance of unrecognized income tax benefits as of March 31, 2013 could decrease by a maximum of $6.7 million in the next 12 months due to the expiration of statutes of limitation and audit settlements.