Schedule I - Condensed Financial Information of Parent Company - Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Assets
Cash and cash equivalents	$ 47,928	$ 3,833
Income taxes receivable	5,672	4,933
Other, net	64,549	44,472
Total current assets	377,479	294,010
Property, plant and equipment, net of accumulated depreciation of $15,706 and $14,583	5,965,149	5,466,009
Other long-term assets	284	356
Total assets	7,939,854	7,298,774	$ 6,865,551
Liabilities and Stockholders’ Equity
Short-term debt	32,000	185,100
Current maturities of long-term debt	575,518	490,268
Accrued interest and taxes	68,206	76,815
Other current liabilities	62,841	47,397
Total current liabilities	977,662	967,481
Long-term debt	2,719,632	2,517,449
Total liabilities	5,819,851	5,545,495
Common stock (no par value; 120,000,000 shares authorized; issued and outstanding 85,834,874 shares)	1,429,941	1,150,552
Accumulated other comprehensive income (loss), net of tax	(79,183)	(99,377)
Retained earnings	698,707	627,523
Total PNMR common stockholders’ equity	2,049,465	1,678,698
Total liabilities and stockholders' equity	7,939,854	7,298,774
PNM Resources
Assets
Cash and cash equivalents	52	79
Intercompany receivables	71,567	79,059
Income taxes receivable	0	4,635
Other, net	5,545	2,876
Total current assets	77,164	86,649
Property, plant and equipment, net of accumulated depreciation of $15,706 and $14,583	23,191	24,313
Investment in subsidiaries	2,631,567	2,197,918
Other long-term assets	58,695	55,077
Total long-term assets	2,713,453	2,277,308
Total assets	2,790,617	2,363,957
Liabilities and Stockholders’ Equity
Short-term debt	12,000	112,100
Short-term debt-affiliate	8,819	40,619
Current maturities of long-term debt	229,948	50,000
Accrued interest and taxes	8,124	5,239
Other current liabilities	29,549	25,450
Total current liabilities	288,440	233,408
Long-term debt	449,909	449,048
Other long-term liabilities	2,803	2,803
Total liabilities	741,152	685,259
Common stock (no par value; 120,000,000 shares authorized; issued and outstanding 85,834,874 shares)	1,429,941	1,150,552
Accumulated other comprehensive income (loss), net of tax	(79,183)	(99,377)
Retained earnings	698,707	627,523
Total PNMR common stockholders’ equity	2,049,465	1,678,698
Total liabilities and stockholders' equity	$ 2,790,617	$ 2,363,957