Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017
Income Tax [Line Items]
Deferred Income Tax Expense		$ 15,339	$ 6,695
Internal Revenue Service (IRS) | Latest Tax Year
Income Tax [Line Items]
Tax Year Closed		2011
NEW MEXICO | Latest Tax Year
Income Tax [Line Items]
Tax Year Closed		2011
TEXAS | Earliest Tax Year
Income Tax [Line Items]
Income Tax Examination, Year under Examination		2007
TEXAS | Latest Tax Year
Income Tax [Line Items]
Income Tax Examination, Year under Examination		2010
ARIZONA | Latest Tax Year
Income Tax [Line Items]
Tax Year Closed		2011
Change in Accounting Method Accounted for as Change in Estimate
Income Tax [Line Items]
Regulatory Asset, Amortization Period		15 years
Deferred Income Tax Expense	$ 1,100	$ 1,700		$ 4,900