Lease Commitments - Schedule of Future Expected Lease Payments (Details) $ in Thousands	Mar. 31, 2020 USD ($)
Financing
Remainder of 2020	$ 2,027
2021	2,631
2022	2,551
2023	2,345
2024	1,786
Later years	2,375
Total minimum lease payments	13,715
Less: Imputed interest	1,235
Lease liabilities as of March 31, 2020	12,480
Operating
Remainder of 2020	20,076
2021	29,316
2022	28,473
2023	19,423
2024	8,833
Later years	35,488
Total minimum lease payments	141,609
Less: Imputed interest	16,343
Lease liabilities as of March 31, 2020	125,266
PNM
Financing
Remainder of 2020	861
2021	1,117
2022	1,082
2023	1,038
2024	712
Later years	1,008
Total minimum lease payments	5,818
Less: Imputed interest	527
Lease liabilities as of March 31, 2020	5,291
Operating
Remainder of 2020	17,386
2021	26,576
2022	26,266
2023	17,735
2024	7,908
Later years	34,466
Total minimum lease payments	130,337
Less: Imputed interest	14,924
Lease liabilities as of March 31, 2020	115,413
TNMP
Financing
Remainder of 2020	1,111
2021	1,441
2022	1,396
2023	1,269
2024	1,074
Later years	1,367
Total minimum lease payments	7,658
Less: Imputed interest	697
Lease liabilities as of March 31, 2020	6,961
Operating
Remainder of 2020	2,279
2021	2,448
2022	1,996
2023	1,508
2024	877
Later years	765
Total minimum lease payments	9,873
Less: Imputed interest	790
Lease liabilities as of March 31, 2020	$ 9,083