Lease Commitments - Narrative (Details) $ in Thousands		11 Months Ended	12 Months Ended
	Jan. 15, 2016 USD ($) MW	Nov. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) Operating_Leases	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Apr. 01, 2015
Lease commitments
Operating lease, option term extensions			2 years
Operating leases, renewal options after original lease term			6 years
Corporate Headquarters [Member]
Lease commitments
Operating lease expense		$ 1,900
Public Service Company of New Mexico [Member]
Lease commitments
Operating lease expense			$ 63,558	$ 76,745	$ 78,306
Public Service Company of New Mexico [Member] | TGP Granada, LLC and its affiliate Complaint [Member]
Lease commitments
Lease ownership in EIP			60.00%
Additional area leased of the EIP						40.00%
Option to purchase leased capacity at fair value			$ 7,700
Public Service Company of New Mexico [Member] | Navajo Nation [Member]
Lease commitments
Number of operating leases set to expire | Operating_Leases			0
Operating leases, period to expiration of the lease			5 years
Annual lease payments			$ 6,000
Public Service Company of New Mexico [Member] | Palo Verde Nuclear Generating Station [Member]
Lease commitments
Rental payments, fixed renewal option period during original terms of leases			50.00%
Lease covenants, restrictions on conveying, transferring, leasing, and dividends (more than)			5.00%
Loss contingency, range of possible loss, portion not accrued			$ 205,800
Public Service Company of New Mexico [Member] | Palo Verde Nuclear Generating Station [Member] | Subsequent Event [Member]
Lease commitments
Loss contingency, range of possible loss, portion not accrued	$ 179,100
Public Service Company of New Mexico [Member] | Palo Verde Nuclear Generating Station, Unit 1 Leases [Member]
Lease commitments
Annual lease payments			33,000
Annual lease payments during renewal period			16,500
Public Service Company of New Mexico [Member] | Palo Verde Nuclear Generating Station, Unit 2 Leases [Member]
Lease commitments
Annual lease payments			23,700
Annual lease payments during renewal period			$ 1,600
Public Service Company of New Mexico [Member] | Palo Verde Nuclear Generating Station, Unit 2 Leases [Member] | Subsequent Event [Member]
Lease commitments
Estimated purchase price of leased asset	$ 78,100
Leased capacity to be purchased (in megawatts) | MW	31.25
Additional capacity to be leased (in megawatts) | MW	32.76
Public Service Company of New Mexico [Member] | Palo Verde Nuclear Generating Station, Unit 2 Leases 32.76 MW [Member] | Subsequent Event [Member]
Lease commitments
Estimated purchase price of leased asset	$ 85,200