Lease Commitments - Schedule of Supplemental Cash Flows Related to Leases (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 9,658	$ 9,891
Operating cash flows from financing leases	27	32
Finance cash flows from financing leases	147	58
Non-cash information related to right-of-use assets obtained in exchange for lease obligations:
Operating leases	0	157,440
Financing leases	4,272	2,904
PNM
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	9,351	9,452
Operating cash flows from financing leases	16	16
Finance cash flows from financing leases	80	25
Non-cash information related to right-of-use assets obtained in exchange for lease obligations:
Operating leases	0	143,816
Financing leases	1,463	1,635
TNMP
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	166	284
Operating cash flows from financing leases	9	17
Finance cash flows from financing leases	51	33
Non-cash information related to right-of-use assets obtained in exchange for lease obligations:
Operating leases	0	12,942
Financing leases	$ 2,802	$ 1,268