Lease Commitments - Schedule of Supplemental Cash Flows Related to Leases (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 26,708	$ 27,225
Operating cash flows from financing leases	94	45
Finance cash flows from financing leases	646	189
Non-cash information related to right-of-use assets obtained in exchange for lease obligations:
Operating leases	0	157,816
Financing leases	11,985	7,402
PNM
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	25,804	26,092
Operating cash flows from financing leases	58	28
Finance cash flows from financing leases	378	113
Non-cash information related to right-of-use assets obtained in exchange for lease obligations:
Operating leases	0	143,816
Financing leases	5,635	3,645
TNMP
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	483	757
Operating cash flows from financing leases	32	17
Finance cash flows from financing leases	215	72
Non-cash information related to right-of-use assets obtained in exchange for lease obligations:
Operating leases	0	12,942
Financing leases	$ 6,309	$ 3,678