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