XML 136 R99.htm IDEA: XBRL DOCUMENT
v3.20.2

EMPLOYEE BENEFIT PLANS - ASSUMED HCCTR (Details) - OPEB - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
HCCTR | 7.60% | 7.60% | 7.90%
Ultimate HCCTR | 4.50% | 4.50% | 4.50%
Effect of a 1 percentage point increase in the HCCTR on: |  |  |
Year-end benefit obligation | $ 49,106 | $ 49,061 | $ 36,260
Total service and interest cost | 2,799 | 2,923 | 2,482
Effect of a 1 percentage point decrease in the HCCTR on: |  |  |
Year-end benefit obligation | (38,844) | (38,747) | (28,743)
Total service and interest costs | $ (2,151) | $ (2,250) | $ (1,937)

X
- Definition Defined Benefit Plan, Effect of One-Percentage Point Decrease in Assumed Health Care Cost Trend Rates [Abstract] + References No definition available. + Details
Name: | njr_DefinedBenefitPlanEffectofOnePercentagePointDecreaseinAssumedHealthCareCostTrendRatesAbstract
Namespace Prefix: | njr_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Defined Benefit Plan, Effect of One-Percentage Point Increase in Assumed Health Care Cost Trend Rates [Abstract] + References No definition available. + Details
Name: | njr_DefinedBenefitPlanEffectofOnePercentagePointIncreaseinAssumedHealthCareCostTrendRatesAbstract
Namespace Prefix: | njr_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Health Care Cost Trend Rate + References No definition available. + Details
Name: | njr_HealthCareCostTrendRate
Namespace Prefix: | njr_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of decrease in accumulated postretirement benefit obligation from one-percentage-point decrease in assumed health care cost trend rate. + References Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (m) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointDecreaseOnAccumulatedPostretirementBenefitObligation1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of decrease in service and interest cost components of net periodic postretirement benefit cost from one-percentage-point decrease in assumed health care cost trend rate. + References Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (m) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointDecreaseOnServiceAndInterestCostComponents1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of increase in accumulated postretirement benefit obligation from one-percentage-point increase in assumed health care cost trend rate. + References Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (m) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnAccumulatedPostretirementBenefitObligation
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of increase in service and interest cost components of net periodic postretirement benefit cost from one-percentage-point increase in assumed health care cost trend rate. + References Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (m) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnServiceAndInterestCostComponents
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Ultimate trend rate for health care cost for defined benefit postretirement plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (l) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanUltimateHealthCareCostTrendRate1
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
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_DefinedBenefitPlansAndOtherPostretirementBenefitPlansTableTextBlockLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |