Income Taxes	6 Months Ended
Jun. 30, 2013
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 jurisdiction for years prior to 2008 and in the state jurisdictions for years prior to 1998. The Company is currently under audit in the federal jurisdiction for tax years 2009 through 2012 and in Texas for 2007. A deficiency notice relating to the Company’s 1998 through 2003 and 2006 and 2007 income tax returns in Arizona challenges a pollution control credit, a research and development credit and the payroll, sales and property apportionment factors. The Company is contesting these adjustments. For the three months ended June 30, 2013 and 2012, the Company’s consolidated effective tax rate was 35.3% and 34.6%, respectively. For the six months ended June 30, 2013 and 2012, the Company's consolidated effective tax rate was 34.3% and 33.4%, respectively. For the twelve months ended June 30, 2013 and 2012, the Company's consolidated effective tax rate was 34.4% and 34.7%, respectively. The Company's consolidated effective tax rate for the three, six and twelve months ended June 30, 2013 and 2012 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.

Income Taxes

6 Months Ended

Jun. 30, 2013

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 jurisdiction for years prior to 2008 and in the state jurisdictions for years prior to 1998. The Company is currently under audit in the federal jurisdiction for tax years 2009 through 2012 and in Texas for 2007. A deficiency notice relating to the Company’s 1998 through 2003 and 2006 and 2007 income tax returns in Arizona challenges a pollution control credit, a research and development credit and the payroll, sales and property apportionment factors. The Company is contesting these adjustments.

For the three months ended June 30, 2013 and 2012, the Company’s consolidated effective tax rate was 35.3% and 34.6%, respectively. For the six months ended June 30, 2013 and 2012, the Company's consolidated effective tax rate was 34.3% and 33.4%, respectively. For the twelve months ended June 30, 2013 and 2012, the Company's consolidated effective tax rate was 34.4% and 34.7%, respectively. The Company's consolidated effective tax rate for the three, six and twelve months ended June 30, 2013 and 2012 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.