FAIR VALUE - DEBT (Details) - USD ($) $ in Thousands		Jun. 30, 2019	Sep. 30, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Capital lease obligations		$ 38,600	$ 35,900
Level 2 | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	[1],[2],[3]	1,207,845	1,172,045
Level 2 | Fair market value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value		1,276,912	1,158,051
NJNG
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt issuance costs		7,700	6,500
NJR
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt issuance costs		$ 1,000	$ 1,100

[1] Excludes capital leases of $38.6 million and $35.9 million as of June 30, 2019 and September 30, 2018, respectively.

[2] Excludes NJNG's debt issuance costs of $7.7 million and $6.5 million as of June 30, 2019 and September 30, 2018, respectively.

[3] Excludes NJR's debt issuance costs of $1 million and $1.1 million as of June 30, 2019 and September 30, 2018, respectively.