XML 60 R45.htm IDEA: XBRL DOCUMENT
v3.10.0.1

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - ACCOUNTING STANDARDS UPDATE (Details) $ in Millions | Jun. 30, 2018 USD ($)
--- | ---
Accounting Standards Update 2017-05 |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |
Deferred gain, unamortized balance | $ (6.8)

X
- Definition Deferred Gain (Loss), Unamortized Amount + References No definition available. + Details
Name: | njr_DeferredGainLossUnamortizedAmount
Namespace Prefix: | njr_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=njr_AccountingStandardsUpdate201705Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |