Commitments and Contingencies, Environmental Contingencies (Details)		1 Months Ended
	Mar. 31, 2012 New Mexico Greenhouse Gas (GHG) Regulations [Member] Regulation	Apr. 30, 2012 Electric Generating Unit (EGU) Mercury and Air Toxics Standards (MATS) Rule [Member] MW
Environmental Requirements [Abstract]
Number of regulations in New Mexico to limit GHG emissions which were repealed in 2012	2
Generating capacity (in MW)		25
Number of years before affected facilities must demonstrate compliance, low end of range (in years)		3 years
Number of years before affected facilities must demonstrate compliance, high end of range (in years)		4 years