FAIR VALUE - DEBT (Details) - USD ($) $ in Thousands		Mar. 31, 2019	Sep. 30, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Capital lease obligations		$ 40,200	$ 35,900
Level 2 | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	[1],[2],[3]	1,172,045	1,172,045
Level 2 | Fair market value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value		1,200,720	1,158,051
NJNG
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt issuance costs		6,400	6,500
NJR
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt issuance costs		$ 1,100	$ 1,100

[1] Excludes NJNG's debt issuance costs of $6.4 million and $6.5 million as of March 31, 2019 and September 30, 2018, respectively.

[2] Excludes NJR's debt issuance costs of $1.1 million for both March 31, 2019 and September 30, 2018.

[3] Excludes capital leases of $40.2 million and $35.9 million as of March 31, 2019 and September 30, 2018, respectively.