Schedule I - Condensed Financial Information of Parent Company (Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Assets
Cash and cash equivalents	$ 46,051	$ 28,274	$ 2,533	$ 8,985
Income taxes receivable	5,845	6,360
Other, net	82,104	58,471
Total current assets	385,570	406,434
Property, plant and equipment, net of accumulated depreciation of $11,276 and $10,251	4,535,372	4,270,006
Other long-term assets	604	1,762
Total assets	6,009,328	5,790,237	5,426,858
Liabilities and Stockholders’ Equity
Short-term debt	250,600	105,600
Current maturities of long-term debt	124,979	332,871
Accrued interest and taxes	58,306	53,863
Other current liabilities	59,494	70,194
Total current liabilities	641,120	704,087
Long-term Debt, net of Unamortized Premiums, Discounts, and Debt Issuance Costs	1,966,969	1,629,514
Total liabilities	4,271,579	3,983,616
Common stock (no par value; 120,000,000 shares authorized; issued and outstanding 79,653,624 shares)	1,166,465	1,173,845
Accumulated other comprehensive income (loss), net of tax	(71,432)	(61,755)	(58,140)	(81,630)
Retained earnings	559,780	609,456
Total PNMR common stockholders’ equity	1,654,813	1,721,546
Total liabilities and stockholders' equity	6,009,328	5,790,237
PNM Resources [Member]
Assets
Cash and cash equivalents	441	382	$ 92	$ 29
Intercompany receivables	102,676	107,619
Income taxes receivable	0	29
Other, net	524	548
Total current assets	103,641	108,578
Property, plant and equipment, net of accumulated depreciation of $11,276 and $10,251	26,707	27,076
Investment in subsidiaries	1,822,593	1,757,650
Other long-term assets	81,168	78,347
Total long-term assets	1,930,468	1,863,073
Total assets	2,034,109	1,971,651
Liabilities and Stockholders’ Equity
Short-term debt	191,600	100,600
Short-term debt-affiliate	8,819	8,819
Current maturities of long-term debt	0	118,607
Accrued interest and taxes	7,780	2,816
Other current liabilities	18,282	16,320
Total current liabilities	226,481	247,162
Long-term Debt, net of Unamortized Premiums, Discounts, and Debt Issuance Costs	149,860	0
Other long-term liabilities	2,955	2,943
Total liabilities	379,296	250,105
Common stock (no par value; 120,000,000 shares authorized; issued and outstanding 79,653,624 shares)	1,166,465	1,173,845
Accumulated other comprehensive income (loss), net of tax	(71,432)	(61,755)
Retained earnings	559,780	609,456
Total PNMR common stockholders’ equity	1,654,813	1,721,546
Total liabilities and stockholders' equity	$ 2,034,109	$ 1,971,651