Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax [Line Items]
Period of Average Annual Book Income Before Taxes	3 years
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax	$ 16,620	$ 17,701
Federal statutory tax rate	35.00%	35.00%	35.00%
Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions	$ 500	$ 300	$ 600
Unrecognized tax benefits, Increase (Decrease) resulting from tax positions taken in prior and current period tax returns.	800	2,100	500
Unrecognized tax benefits that would impact effective tax rate	3,600
Unrecognized tax benefits, interest on income taxes expense (benefit)	200	100	$ 200
Unrecognized tax benefits, income tax penalties and interest accrued	700	500
Internal Revenue Service (IRS)
Income Tax [Line Items]
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities	2,800
Tax Credit Carryforward, Amount	$ 34,100
Live Of Tax Loss Carrforwards	20 years
State and Local Jurisdiction
Income Tax [Line Items]
Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions	$ 800
Tax Credit Carryforward, Amount	$ 1,100
Live Of Tax Loss Carrforwards	5 years
Minimum | TEXAS
Income Tax [Line Items]
Income Tax Examination, Year under Examination	2007
Minimum | ARIZONA
Income Tax [Line Items]
Income Tax Examination, Year under Examination	2009
Maximum | Internal Revenue Service (IRS)
Income Tax [Line Items]
Tax Year Closed	2010
Maximum | NEW MEXICO
Income Tax [Line Items]
Tax Year Closed	2010
Maximum | TEXAS
Income Tax [Line Items]
Income Tax Examination, Year under Examination	2011
Maximum | ARIZONA
Income Tax [Line Items]
Income Tax Examination, Year under Examination	2012
Change in Accounting Method Accounted for as Change in Estimate | Internal Revenue Service (IRS)
Income Tax [Line Items]
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities		4,500
Tax credit taken | ARIZONA
Income Tax [Line Items]
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities		400
Increase (Decrease) in Unrecognized Tax Position of Prior Years Recorded, net	$ (1,300)	$ 1,300
Unrecognized Tax Benefits, Increase Resulting from Settlements with Taxing Authorities	$ 400