Income Taxes	6 Months Ended
Jun. 30, 2015
Components of Income Tax Expense (Benefit), Continuing Operations [Abstract]
Income Taxes	Income Taxes The Company files income tax returns in the United States ("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 and New Mexico jurisdictions for years prior to 2010. The Company is currently under audit in Texas for tax years 2007 through 2011 and in Arizona for tax years 2009 through 2012. For the three months ended June 30, 2015 and 2014, the Company’s effective tax rate was 31.1% and 32.9%, respectively. For the six months ended June 30, 2015 and 2014, the Company’s effective tax rate was 30.0% and 31.9%, respectively. For the twelve months ended June 30, 2015 and 2014, the Company's effective tax rate was 30.3% and 32.0%, respectively. The Company's effective tax rate for all time periods differs from the federal statutory tax rate of 35.0% primarily due to the allowance for equity funds used during construction and state income taxes. The Company’s effective tax rate for the six months ended June 30, 2015 also differs from the federal statutory tax rate of 35.0% due to capital gains in the qualified decommissioning trust realized in the first quarter of 2015, which are taxed at a federal tax rate of 20.0%. In June 2015, legislation was approved in Texas which permanently reduced the Texas Franchise Tax rate to 0.75% tax on taxable margins down from an interim rate of 0.95%. The rate reduction is applicable to tax reports originally due on or after January 1, 2016 and is retroactive to January 1, 2015 tax accruals. The implementation of this rate change in June 2015 did not have a material impact on the financial statements of the Company.

Income Taxes

6 Months Ended

Jun. 30, 2015

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

The Company files income tax returns in the United States ("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 and New Mexico jurisdictions for years prior to 2010. The Company is currently under audit in Texas for tax years 2007 through 2011 and in Arizona for tax years 2009 through 2012.

For the three months ended June 30, 2015 and 2014, the Company’s effective tax rate was 31.1% and 32.9%, respectively. For the six months ended June 30, 2015 and 2014, the Company’s effective tax rate was 30.0% and 31.9%, respectively. For the twelve months ended June 30, 2015 and 2014, the Company's effective tax rate was 30.3% and 32.0%, respectively. The Company's effective tax rate for all time periods differs from the federal statutory tax rate of 35.0% primarily due to the allowance for equity funds used during construction and state income taxes. The Company’s effective tax rate for the six months ended June 30, 2015 also differs from the federal statutory tax rate of 35.0% due to capital gains in the qualified decommissioning trust realized in the first quarter of 2015, which are taxed at a federal tax rate of 20.0%.

In June 2015, legislation was approved in Texas which permanently reduced the Texas Franchise Tax rate to 0.75% tax on taxable margins down from an interim rate of 0.95%. The rate reduction is applicable to tax reports originally due on or after January 1, 2016 and is retroactive to January 1, 2015 tax accruals. The implementation of this rate change in June 2015 did not have a material impact on the financial statements of the Company.