Schedule I - Condensed Financial Information of Parent Company - Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Assets
Cash and cash equivalents	$ 4,522	$ 46,051	$ 28,274	$ 2,533
Other, net	73,444	82,104
Total current assets	378,039	385,570
Property, plant and equipment, net of accumulated depreciation of $12,291 and $11,276	4,904,715	4,535,372
Other long-term assets	547	604
Total assets	6,471,080	6,009,328	5,790,237
Liabilities and Stockholders’ Equity
Short-term debt	287,100	250,600
Accrued interest and taxes	61,871	58,306
Other current liabilities	59,314	59,494
Total current liabilities	805,108	641,120
Long-term debt	2,119,364	1,966,969
Total liabilities	4,714,679	4,271,579
Common stock (no par value; 120,000,000 shares authorized; issued and outstanding 79,653,624 shares)	1,163,661	1,166,465
Accumulated other comprehensive income (loss), net of tax	(92,451)	(71,432)
Retained earnings	604,742	559,780
Total PNMR common stockholders’ equity	1,675,952	1,654,813
Total liabilities and stockholders' equity	6,471,080	6,009,328
PNM Resources [Member]
Assets
Cash and cash equivalents	54	441	$ 382	$ 92
Intercompany receivables	92,234	102,676
Other, net	233	524
Total current assets	92,521	103,641
Property, plant and equipment, net of accumulated depreciation of $12,291 and $11,276	26,366	26,707
Investment in subsidiaries	1,986,276	1,822,593
Other long-term assets	79,314	81,168
Total long-term assets	2,091,956	1,930,468
Total assets	2,184,477	2,034,109
Liabilities and Stockholders’ Equity
Short-term debt	226,100	191,600
Short-term debt-affiliate	8,819	8,819
Accrued interest and taxes	1,333	7,780
Other current liabilities	19,374	18,282
Total current liabilities	255,626	226,481
Long-term debt	249,895	149,860
Other long-term liabilities	3,004	2,955
Total liabilities	508,525	379,296
Common stock (no par value; 120,000,000 shares authorized; issued and outstanding 79,653,624 shares)	1,163,661	1,166,465
Accumulated other comprehensive income (loss), net of tax	(92,451)	(71,432)
Retained earnings	604,742	559,780
Total PNMR common stockholders’ equity	1,675,952	1,654,813
Total liabilities and stockholders' equity	$ 2,184,477	$ 2,034,109