Income Taxes	6 Months Ended
Jun. 30, 2013
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The effective income tax rate for the three months ended June 30, 2013 and 2012 was 36.2% and 38.0%, respectively. The effective income tax rate for the six months ended June 30, 2013 and 2012 was 37.2% and 37.9%, 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. The decrease in the effective income tax rate for the three months ended June 30, 2013 was primarily due to a reduction in uncertain income tax positions recognized for closing statutes. As of June 30, 2013, the Company had a gross liability for uncertain income tax benefits of $20.1 million, $15.0 million of which, if recognized, would impact the effective income tax rate. During the second quarter of 2013, the Company recognized a benefit of $1.9 million related to closing statutes. 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 June 30, 2013 could decrease by a maximum of $4.8 million in the next 12 months due to the expiration of statutes of limitation and audit settlements.

Income Taxes

6 Months Ended

Jun. 30, 2013

The effective income tax rate for the three months ended June 30, 2013 and 2012 was 36.2% and 38.0%, respectively. The effective income tax rate for the six months ended June 30, 2013 and 2012 was 37.2% and 37.9%, 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. The decrease in the effective income tax rate for the three months ended June 30, 2013 was primarily due to a reduction in uncertain income tax positions recognized for closing statutes.

As of June 30, 2013, the Company had a gross liability for uncertain income tax benefits of $20.1 million, $15.0 million of which, if recognized, would impact the effective income tax rate. During the second quarter of 2013, the Company recognized a benefit of $1.9 million related to closing statutes. 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 June 30, 2013 could decrease by a maximum of $4.8 million in the next 12 months due to the expiration of statutes of limitation and audit settlements.