Summary of the Business and Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2016

Accounting Policies [Abstract]

Schedule of Average Rates Used Allocated Between Depreciation Expense and Construction Expense Projects Based on Use of Equipment

Average straight-line rates used were as follows:

	Year ended December 31
	2016		2015		2014
PNM
Electric plant	2.33	%	2.27	%	2.26	%
Common, intangible, and general plant	5.40	%	4.66	%	4.64	%
TNMP	3.66	%	3.65	%	3.59	%

Schedule of Inventory

Inventories consisted of the following at December 31:

	PNMR				PNM				TNMP
	2016		2015		2016		2015		2016		2015
	(In thousands)
Coal	$	19,940	$	18,356	$	19,940	$	18,356	$	—	$	—
Materials and supplies	53,087		49,030		44,461		42,121		8,626		6,909
	$	73,027	$	67,386	$	64,401	$	60,477	$	8,626	$	6,909