XML 67 R52.htm IDEA: XBRL DOCUMENT
v3.10.0.1

DERIVATIVE INSTRUMENTS - BROKER MARGIN DEPOSITS (Details) - USD ($) $ in Thousands | Jun. 30, 2018 | Sep. 30, 2017
--- | --- | ---
Natural Gas Distribution |  |
Derivative [Line Items] |  |
Broker margin - Current assets | $ 1,845 | $ 2,661
Energy Services |  |
Derivative [Line Items] |  |
Broker margin - Current assets | $ 51,296 | $ 23,166

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_DerivativeLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of other receivables due from broker-dealers or clearing organizations. + References No definition available. + Details
Name: | us-gaap_OtherReceivablesFromBrokerDealersAndClearingOrganizations
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=njr_NaturalGasDistributionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=njr_EnergyServicesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |