Income Taxes	3 Months Ended
Mar. 31, 2019
Components of Income Tax Expense (Benefit), Continuing Operations [Abstract]
Income Taxes	Income Taxes The Company files income tax returns in the U.S. federal jurisdiction and in the states of Texas, New Mexico and Arizona. The Company is no longer subject to tax examination by the taxing authorities in the federal, Texas, Arizona, and New Mexico jurisdictions for years prior to 2014. For the three months ended March 31, 2019 and 2018, the Company’s effective tax rate was 23.8% and 30.5%, respectively. For the twelve months ended March 31, 2019 and 2018, the Company's effective tax rate was 24.3% and 34.5%, respectively. The federal statutory tax rate is 21% in 2019 and in 2018, and 35.0% in 2017. The Company's effective tax rate for the three months ended March 31, 2019 differs from the Company's effective tax rate for the three months ended March 31, 2018 due to lower values of stock incentives vested and other permanent differences. The Company's effective tax rate for the twelve months ended March 31, 2019 differs from the Company's effective tax rate for the twelve months ended March 31, 2018 due to the change in the federal income tax rate partially offset by an increase in state tax reserves and other permanent differences.

Income Taxes

3 Months Ended

Mar. 31, 2019

Components of Income Tax Expense (Benefit), Continuing Operations [Abstract]

The Company files income tax returns in the U.S. federal jurisdiction and in the states of Texas, New Mexico and Arizona. The Company is no longer subject to tax examination by the taxing authorities in the federal, Texas, Arizona, and New Mexico jurisdictions for years prior to 2014.

For the three months ended March 31, 2019 and 2018, the Company’s effective tax rate was 23.8% and 30.5%, respectively. For the twelve months ended March 31, 2019 and 2018, the Company's effective tax rate was 24.3% and 34.5%, respectively. The federal statutory tax rate is 21% in 2019 and in 2018, and 35.0% in 2017. The Company's effective tax rate for the three months ended March 31, 2019 differs from the Company's effective tax rate for the three months ended March 31, 2018 due to lower values of stock incentives vested and other permanent differences. The Company's effective tax rate for the twelve months ended March 31, 2019 differs from the Company's effective tax rate for the twelve months ended March 31, 2018 due to the change in the federal income tax rate partially offset by an increase in state tax reserves and other permanent differences.