Lease Commitments - Schedule of Supplemental Cash Flows Related to Leases (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 17,125	$ 17,494
Operating cash flows from financing leases	59	38
Finance cash flows from financing leases	360	130
Non-cash information related to right-of-use assets obtained in exchange for lease obligations:
Operating leases	0	157,440
Financing leases	8,513	4,821
PNM
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	16,511	16,704
Operating cash flows from financing leases	36	18
Finance cash flows from financing leases	207	54
Non-cash information related to right-of-use assets obtained in exchange for lease obligations:
Operating leases	0	143,816
Financing leases	3,703	2,516
TNMP
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	331	529
Operating cash flows from financing leases	20	20
Finance cash flows from financing leases	120	76
Non-cash information related to right-of-use assets obtained in exchange for lease obligations:
Operating leases	0	12,942
Financing leases	$ 4,802	$ 2,305