Fair Value of Derivative and Other Financial Instruments - Items not Recorded at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
PNMR [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 2,264,869	$ 2,173,117
Investment in PVNGS lessor notes	8,947	32,836
Other investments	1,269	2,375
PNMR [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	2,091,948	1,962,385
Investment in PVNGS lessor notes	8,587	31,232
Other investments	604	1,762
PNMR [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	0	0
Investment in PVNGS lessor notes	0	0
Other investments	604	639
PNMR [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	2,264,869	2,173,117
Investment in PVNGS lessor notes	0	0
Other investments	0	0
PNMR [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	0	0
Investment in PVNGS lessor notes	8,947	32,836
Other investments	665	1,736
Public Service Company of New Mexico [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	1,703,209	1,624,222
Investment in PVNGS lessor notes	8,947	32,836
Other investments	366	397
Public Service Company of New Mexico [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	1,580,677	1,482,537
Investment in PVNGS lessor notes	8,587	31,232
Other investments	366	397
Public Service Company of New Mexico [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	0	0
Investment in PVNGS lessor notes	0	0
Other investments	366	397
Public Service Company of New Mexico [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	1,703,209	1,624,222
Investment in PVNGS lessor notes	0	0
Other investments	0	0
Public Service Company of New Mexico [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	0	0
Investment in PVNGS lessor notes	8,947	32,836
Other investments	0	0
Texas-New Mexico Power Company [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	411,661	427,356
Other investments	238	242
Texas-New Mexico Power Company [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	361,411	361,241
Other investments	238	242
Texas-New Mexico Power Company [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	0	0
Other investments	238	242
Texas-New Mexico Power Company [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	411,661	427,356
Other investments	0	0
Texas-New Mexico Power Company [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	0	0
Other investments	$ 0	$ 0