Lease Commitments - Finance Lease Balance Sheet Information (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing leases:
Non-utility property	$ 14,299	$ 10,028
Accumulated depreciation	(1,527)	(973)
Non-utility property, net	12,772	9,055
Other current liabilities	2,298	1,637
Other deferred credits	10,182	7,102
PNM
Financing leases:
Non-utility property	6,320	4,857
Accumulated depreciation	(729)	(482)
Non-utility property, net	5,591	4,375
Other current liabilities	975	722
Other deferred credits	4,316	3,333
TNMP
Financing leases:
Non-utility property	7,712	4,910
Accumulated depreciation	(756)	(466)
Non-utility property, net	6,956	4,444
Other current liabilities	1,255	850
Other deferred credits	$ 5,706	$ 3,597