Lease Commitments (Details) - Public Service Company of New Mexico [Member] $ in Millions	3 Months Ended
	Mar. 31, 2015 USD ($)	Sep. 30, 2015 USD ($) MW	Sep. 18, 2015 USD ($) MW	Apr. 01, 2015
Operating Leased Assets [Line Items]
Public utilities, lease ownership percentage in EIP	60.00%
Public Utilities, Additional ownership percentage in EIP purchased				40.00%
Public utilities, option to purchase leased capacity at fair value	$ 7.7
Palo Verde Nuclear Generating Station, Unit 2 Leases 31.2494 MW [Member]
Operating Leased Assets [Line Items]
Purchase price of leased asset to be paid		$ 78.1
Palo Verde Nuclear Generating Station, Unit 2 Leases [Member]
Operating Leased Assets [Line Items]
Leased capacity to be purchased (in megawatts) | MW			32.76
Palo Verde Nuclear Generating Station, Unit 2 Leases, January 15, 2016 [Member]
Operating Leased Assets [Line Items]
Leased capacity to be purchased (in megawatts) | MW		31.25
Palo Verde Nuclear Generating Station, Unit 2 Leases 32.76 MW [Member]
Operating Leased Assets [Line Items]
Purchase price of leased asset to be paid			$ 85.2