Lease Commitments - Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Lease, Cost [Line Items]
Operating lease cost:	$ 7,237	$ 7,429
Amounts capitalized	(654)	(785)
Total operating lease expense	6,583	6,644
Financing lease cost:
Amortization of right-of-use assets	1,511	1,167
Interest on lease liabilities	141	139
Amounts capitalized	(1,213)	(993)
Total financing lease expense	439	313
Variable lease expense	106	63
Short-term lease expense	1,169	132
Total lease expense for the period	8,297	7,152
Cooling Towers
Financing lease cost:
Short-term lease expense	1,100	1,100
Increase reimbursements	1,100	1,100
PNM
Lease, Cost [Line Items]
Operating lease cost:	6,683	6,735
Amounts capitalized	(185)	(226)
Total operating lease expense	6,498	6,509
Financing lease cost:
Amortization of right-of-use assets	732	532
Interest on lease liabilities	68	62
Amounts capitalized	(497)	(368)
Total financing lease expense	303	226
Variable lease expense	106	63
Short-term lease expense	1,132	124
Total lease expense for the period	8,039	6,922
TNMP
Lease, Cost [Line Items]
Operating lease cost:	528	653
Amounts capitalized	(469)	(559)
Total operating lease expense	59	94
Financing lease cost:
Amortization of right-of-use assets	757	613
Interest on lease liabilities	73	76
Amounts capitalized	(717)	(625)
Total financing lease expense	113	64
Variable lease expense	0	0
Short-term lease expense	0	2
Total lease expense for the period	$ 172	$ 160