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PENSION AND OTHER POSTRETIREMENT BENEFITS - FAIR VALUE OF PLAN ASSETS (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2018
Pension Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 216,065 $ 189,542 $ 287,220
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 216,065 189,542  
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year $ 287,220 216,065  
Pension Benefits | Minimum      
Defined Benefit Plan Disclosure [Line Items]      
Fund Valuations Lag Period 90 days    
Pension Benefits | Maximum      
Defined Benefit Plan Disclosure [Line Items]      
Fund Valuations Lag Period 120 days    
Pension Benefits | Fair Value, Inputs, Level 1, 2 and 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 29,782 29,782 119,843
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 29,782    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 119,843 29,782  
Pension Benefits | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 19,049 19,049 109,737
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 19,049    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 109,737 19,049  
Pension Benefits | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 1,522 1,522 1,653
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 1,522    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 1,653 1,522  
Pension Benefits | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 9,211 9,714 8,453
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 9,211 9,714  
Actual return on plan assets:      
Relating to assets still held at the reporting date (53) 245  
Relating to assets sold during the period 13 12  
Purchases, Sales and Settlements (718) (760)  
Fair Value of Plan Assets at End of Year 8,453 9,211  
Pension Benefits | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 186,283 186,283 167,377
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 186,283    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 167,377 186,283  
Pension Benefits | Cash | Fair Value, Inputs, Level 1, 2 and 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 72 72 92,224
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 72    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 92,224 72  
Pension Benefits | Cash | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 72 72 92,224
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 72    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 92,224 72  
Pension Benefits | Cash | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
Pension Benefits | Cash | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
Pension Benefits | STIF-Type Instrument | Fair Value, Inputs, Level 1, 2 and 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 1,522 1,522 1,653
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 1,522    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 1,653 1,522  
Pension Benefits | STIF-Type Instrument | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
Pension Benefits | STIF-Type Instrument | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 1,522 1,522 1,653
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 1,522    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 1,653 1,522  
Pension Benefits | STIF-Type Instrument | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 $ 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
Pension Benefits | U.S. equity securities | Minimum      
Actual return on plan assets:      
Target plan allocation     40.00%
Pension Benefits | U.S. equity securities | Maximum      
Actual return on plan assets:      
Target plan allocation     70.00%
Pension Benefits | U.S. Large-Cap | Fair Value, Inputs, Level 1, 2 and 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 13,526 13,526 $ 13,684
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 13,526    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 13,684 13,526  
Pension Benefits | U.S. Large-Cap | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 13,526 13,526 13,684
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 13,526    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 13,684 13,526  
Pension Benefits | U.S. Large-Cap | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
Pension Benefits | U.S. Large-Cap | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
Pension Benefits | U.S. Mid-Cap | Fair Value, Inputs, Level 1, 2 and 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 1,701 1,701 1,502
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 1,701    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 1,502 1,701  
Pension Benefits | U.S. Mid-Cap | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 1,701 1,701 1,502
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 1,701    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 1,502 1,701  
Pension Benefits | U.S. Mid-Cap | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
Pension Benefits | U.S. Mid-Cap | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 $ 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
Pension Benefits | Small Cap | Fair Value, Inputs, Level 1, 2 and 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 490 490  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 490    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year   490  
Pension Benefits | Small Cap | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 490 490  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 490    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year   490  
Pension Benefits | Small Cap | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year   0  
Pension Benefits | Small Cap | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year   0  
Pension Benefits | International equity securities | Minimum      
Actual return on plan assets:      
Target plan allocation     10.00%
Pension Benefits | International equity securities | Maximum      
Actual return on plan assets:      
Target plan allocation     25.00%
Pension Benefits | International equity securities | Fair Value, Inputs, Level 1, 2 and 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 3,260 3,260 $ 2,327
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 3,260    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 2,327 3,260  
Pension Benefits | International equity securities | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 3,260 3,260 2,327
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 3,260    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 2,327 3,260  
Pension Benefits | International equity securities | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
Pension Benefits | International equity securities | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
Pension Benefits | Guaranteed Insurance Contract | Fair Value, Inputs, Level 1, 2 and 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 9,211 9,211 8,453
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 9,211    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 8,453 9,211  
Pension Benefits | Guaranteed Insurance Contract | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
Pension Benefits | Guaranteed Insurance Contract | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
Pension Benefits | Guaranteed Insurance Contract | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 9,211 9,714 $ 8,453
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 9,211 9,714  
Actual return on plan assets:      
Relating to assets still held at the reporting date (53) 245  
Relating to assets sold during the period 13 12  
Purchases, Sales and Settlements (718) (760)  
Fair Value of Plan Assets at End of Year 8,453 9,211  
Pension Benefits | Other investments | Minimum      
Actual return on plan assets:      
Target plan allocation     0.00%
Pension Benefits | Other investments | Maximum      
Actual return on plan assets:      
Target plan allocation     20.00%
Pension Benefits | Private Equity Funds and Common or Collective Trust Funds, Real Estate [Member] | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 16,924 16,924 $ 18,604
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 16,924    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 18,604 16,924  
Pension Benefits | Private Equity Funds | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0 0  
Actual return on plan assets:      
Relating to assets still held at the reporting date 0 0  
Relating to assets sold during the period 0 0  
Purchases, Sales and Settlements 0 0  
Fair Value of Plan Assets at End of Year 0 0  
Pension Benefits | Private Equity Funds | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 7,111 7,111 8,867
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 7,111    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 8,867 7,111  
Pension Benefits | Real Estate | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0 0  
Actual return on plan assets:      
Relating to assets still held at the reporting date 0 0  
Relating to assets sold during the period 0 0  
Purchases, Sales and Settlements 0 0  
Fair Value of Plan Assets at End of Year 0 0  
Pension Benefits | Real Estate | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 9,813 9,813 9,737
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 9,813    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 9,737 9,813  
Pension Benefits | Other Common or Collective Trust Funds [Member] | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 169,359 169,359 148,773
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 169,359    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 148,773 169,359  
Pension Benefits | Common/Collective Trust Funds | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 477 477 696
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 477    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 696 477  
Pension Benefits | Common/Collective Trust Funds - U.S. | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 75,699 75,699 63,418
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 75,699    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 63,418 75,699  
Pension Benefits | Common/Collective Trust Funds - International | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 39,077 39,077 33,391
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 39,077    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 33,391 39,077  
Pension Benefits | Common/Collective Trust Funds | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 54,106 54,106 51,268
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 54,106    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 51,268 54,106  
Other Postretirement Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 57,922 50,532 70,531
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 57,922 50,532  
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 70,531 57,922  
Other Postretirement Benefits | Fair Value, Inputs, Level 1, 2 and 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 864 864 17,542
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 864    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 17,542 864  
Other Postretirement Benefits | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 864 864 17,542
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 864    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 17,542 864  
Other Postretirement Benefits | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
Other Postretirement Benefits | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
Other Postretirement Benefits | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 57,058 57,058 52,989
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 57,058    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 52,989 57,058  
Other Postretirement Benefits | Cash | Fair Value, Inputs, Level 1, 2 and 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 16,720   16,720
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 16,720    
Other Postretirement Benefits | Cash | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 16,720   16,720
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 16,720    
Other Postretirement Benefits | Cash | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0   0
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0    
Other Postretirement Benefits | Cash | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0   $ 0
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0    
Other Postretirement Benefits | U.S. equity securities | Minimum      
Actual return on plan assets:      
Target plan allocation     55.00%
Other Postretirement Benefits | U.S. equity securities | Maximum      
Actual return on plan assets:      
Target plan allocation     75.00%
Other Postretirement Benefits | International equity securities | Minimum      
Actual return on plan assets:      
Target plan allocation     10.00%
Other Postretirement Benefits | International equity securities | Maximum      
Actual return on plan assets:      
Target plan allocation     20.00%
Other Postretirement Benefits | Fixed income investments | Minimum      
Actual return on plan assets:      
Target plan allocation     25.00%
Other Postretirement Benefits | Fixed income investments | Maximum      
Actual return on plan assets:      
Target plan allocation     45.00%
Other Postretirement Benefits | Other investments | Minimum      
Actual return on plan assets:      
Target plan allocation     0.00%
Other Postretirement Benefits | Other investments | Maximum      
Actual return on plan assets:      
Target plan allocation     7.00%
Other Postretirement Benefits | Mutual Funds - REITS | Fair Value, Inputs, Level 1, 2 and 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 864 864 $ 822
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 864    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 822 864  
Other Postretirement Benefits | Mutual Funds - REITS | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 864 864 822
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 864    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 822 864  
Other Postretirement Benefits | Mutual Funds - REITS | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
Other Postretirement Benefits | Mutual Funds - REITS | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
Other Postretirement Benefits | Company Owned Life Insurance | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 15,307 15,307 13,885
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 15,307    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 13,885 15,307  
Other Postretirement Benefits | Common/Collective Trust Funds - U.S. | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 15,101 15,101 14,069
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 15,101    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 14,069 15,101  
Other Postretirement Benefits | Common/Collective Trust Funds - International | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 11,378 11,378 9,720
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 11,378    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 9,720 11,378  
Other Postretirement Benefits | Common/Collective Trust Funds | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 15,272 15,272 15,315
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 15,272    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 15,315 15,272  
South Jersey Gas Company | U.S. Small-Cap | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year   0  
South Jersey Gas Company | Pension Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 174,277 154,729 160,285
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 174,277 154,729  
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 160,285 174,277  
South Jersey Gas Company | Pension Benefits | Fair Value, Inputs, Level 1, 2 and 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 24,021 24,021 22,718
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 24,021    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 22,718 24,021  
South Jersey Gas Company | Pension Benefits | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 15,364 15,364 14,412
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 15,364    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 14,412 15,364  
South Jersey Gas Company | Pension Benefits | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 1,228 1,228 1,359
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 1,228    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 1,359 1,228  
South Jersey Gas Company | Pension Benefits | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 7,429 7,930 6,947
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 7,429 7,930  
Actual return on plan assets:      
Relating to assets still held at the reporting date 98 103  
Relating to assets sold during the period 11 9  
Purchases, Sales and Settlements (591) (613)  
Fair Value of Plan Assets at End of Year 6,947 7,429  
South Jersey Gas Company | Pension Benefits | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 150,256 150,256 137,567
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 150,256    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 137,567 150,256  
South Jersey Gas Company | Pension Benefits | Cash | Fair Value, Inputs, Level 1, 2 and 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 58 58 19
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 58    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 19 58  
South Jersey Gas Company | Pension Benefits | Cash | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 58 58 19
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 58    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 19 58  
South Jersey Gas Company | Pension Benefits | Cash | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
South Jersey Gas Company | Pension Benefits | Cash | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
South Jersey Gas Company | Pension Benefits | STIF-Type Instrument | Fair Value, Inputs, Level 1, 2 and 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 1,228 1,228 1,359
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 1,228    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 1,359 1,228  
South Jersey Gas Company | Pension Benefits | STIF-Type Instrument | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
South Jersey Gas Company | Pension Benefits | STIF-Type Instrument | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 1,228 1,228 1,359
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 1,228    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 1,359 1,228  
South Jersey Gas Company | Pension Benefits | STIF-Type Instrument | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
South Jersey Gas Company | Pension Benefits | U.S. Large-Cap | Fair Value, Inputs, Level 1, 2 and 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 10,910 10,910 11,247
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 10,910    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 11,247 10,910  
South Jersey Gas Company | Pension Benefits | U.S. Large-Cap | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 10,910 10,910 11,247
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 10,910    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 11,247 10,910  
South Jersey Gas Company | Pension Benefits | U.S. Large-Cap | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
South Jersey Gas Company | Pension Benefits | U.S. Large-Cap | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
South Jersey Gas Company | Pension Benefits | U.S. Mid-Cap | Fair Value, Inputs, Level 1, 2 and 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 1,372 1,372 1,234
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 1,372    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 1,234 1,372  
South Jersey Gas Company | Pension Benefits | U.S. Mid-Cap | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 1,372 1,372 1,234
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 1,372    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 1,234 1,372  
South Jersey Gas Company | Pension Benefits | U.S. Mid-Cap | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
South Jersey Gas Company | Pension Benefits | U.S. Mid-Cap | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
South Jersey Gas Company | Pension Benefits | U.S. Small-Cap | Fair Value, Inputs, Level 1, 2 and 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 2,629 2,629  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 2,629    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year   2,629  
South Jersey Gas Company | Pension Benefits | U.S. Small-Cap | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 2,629 2,629  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 2,629    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year   2,629  
South Jersey Gas Company | Pension Benefits | U.S. Small-Cap | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year   0  
South Jersey Gas Company | Pension Benefits | Small Cap | Fair Value, Inputs, Level 1, 2 and 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 395 395  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 395    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year   395  
South Jersey Gas Company | Pension Benefits | Small Cap | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 395 395  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 395    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year   395  
South Jersey Gas Company | Pension Benefits | Small Cap | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year   0  
South Jersey Gas Company | Pension Benefits | Small Cap | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year   0  
South Jersey Gas Company | Pension Benefits | International equity securities | Fair Value, Inputs, Level 1, 2 and 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 1,912   1,912
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 1,912    
South Jersey Gas Company | Pension Benefits | International equity securities | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 1,912   1,912
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 1,912    
South Jersey Gas Company | Pension Benefits | International equity securities | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0   0
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0    
South Jersey Gas Company | Pension Benefits | International equity securities | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0   0
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0    
South Jersey Gas Company | Pension Benefits | Guaranteed Insurance Contract | Fair Value, Inputs, Level 1, 2 and 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 7,429 7,429 6,947
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 7,429    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 6,947 7,429  
South Jersey Gas Company | Pension Benefits | Guaranteed Insurance Contract | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
South Jersey Gas Company | Pension Benefits | Guaranteed Insurance Contract | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
South Jersey Gas Company | Pension Benefits | Guaranteed Insurance Contract | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 7,429 7,930 6,947
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 7,429 7,930  
Actual return on plan assets:      
Relating to assets still held at the reporting date 98 103  
Relating to assets sold during the period 11 9  
Purchases, Sales and Settlements (591) (613)  
Fair Value of Plan Assets at End of Year 6,947 7,429  
South Jersey Gas Company | Pension Benefits | Private Equity Funds and Common or Collective Trust Funds, Real Estate [Member] | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 13,655 13,655 15,291
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 13,655    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 15,291 13,655  
South Jersey Gas Company | Pension Benefits | Private Equity Funds | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0 0  
Actual return on plan assets:      
Relating to assets still held at the reporting date 0 0  
Relating to assets sold during the period 0 0  
Purchases, Sales and Settlements 0 0  
Fair Value of Plan Assets at End of Year 0 0  
South Jersey Gas Company | Pension Benefits | Private Equity Funds | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 5,735 5,735 7,288
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 5,735    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 7,288 5,735  
South Jersey Gas Company | Pension Benefits | Real Estate | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0 0  
Actual return on plan assets:      
Relating to assets still held at the reporting date 0 0  
Relating to assets sold during the period 0 0  
Purchases, Sales and Settlements 0 0  
Fair Value of Plan Assets at End of Year 0 0  
South Jersey Gas Company | Pension Benefits | Real Estate | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 7,920 7,920 8,003
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 7,920    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 8,003 7,920  
South Jersey Gas Company | Pension Benefits | Other Common or Collective Trust Funds [Member] | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 136,601 136,601 122,276
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 136,601    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 122,276 136,601  
South Jersey Gas Company | Pension Benefits | Common/Collective Trust Funds | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 385 385 572
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 385    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 572 385  
South Jersey Gas Company | Pension Benefits | Common/Collective Trust Funds - U.S. | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 61,057 61,057 52,123
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 61,057    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 52,123 61,057  
South Jersey Gas Company | Pension Benefits | Common/Collective Trust Funds - International | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 31,519 31,519 27,444
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 31,519    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 27,444 31,519  
South Jersey Gas Company | Pension Benefits | Common/Collective Trust Funds | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 43,640 43,640 42,137
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 43,640    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 42,137 43,640  
South Jersey Gas Company | Other Postretirement Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 52,663 45,948 49,770
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 52,663 45,948  
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 49,770 52,663  
South Jersey Gas Company | Other Postretirement Benefits | Fair Value, Inputs, Level 1, 2 and 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 777 777 1,599
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 777    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 1,599 777  
South Jersey Gas Company | Other Postretirement Benefits | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 777 777 1,599
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 777    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 1,599 777  
South Jersey Gas Company | Other Postretirement Benefits | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
South Jersey Gas Company | Other Postretirement Benefits | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
South Jersey Gas Company | Other Postretirement Benefits | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 51,886 51,886 48,171
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 51,886    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 48,171 51,886  
South Jersey Gas Company | Other Postretirement Benefits | Cash | Fair Value, Inputs, Level 1, 2 and 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 859   859
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 859    
South Jersey Gas Company | Other Postretirement Benefits | Cash | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 859   859
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 859    
South Jersey Gas Company | Other Postretirement Benefits | Cash | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0   0
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0    
South Jersey Gas Company | Other Postretirement Benefits | Cash | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0   0
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0    
South Jersey Gas Company | Other Postretirement Benefits | Mutual Funds - REITS | Fair Value, Inputs, Level 1, 2 and 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 777 777 740
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 777    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 740 777  
South Jersey Gas Company | Other Postretirement Benefits | Mutual Funds - REITS | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 777 777 740
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 777    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 740 777  
South Jersey Gas Company | Other Postretirement Benefits | Mutual Funds - REITS | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
South Jersey Gas Company | Other Postretirement Benefits | Mutual Funds - REITS | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0 0 0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 0    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 0 0  
South Jersey Gas Company | Other Postretirement Benefits | Company Owned Life Insurance | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 14,362 14,362 13,027
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 14,362    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 13,027 14,362  
South Jersey Gas Company | Other Postretirement Benefits | Common/Collective Trust Funds - U.S. | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 13,572 13,572 12,645
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 13,572    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 12,645 13,572  
South Jersey Gas Company | Other Postretirement Benefits | Common/Collective Trust Funds - International | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 10,226 10,226 8,735
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 10,226    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 8,735 10,226  
South Jersey Gas Company | Other Postretirement Benefits | Corporate Debt Securities | Fair Value Measured at Net Asset Value Per Share [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 13,726 13,726 $ 13,764
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 13,726    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year 13,764 13,726  
Investments Classified As Level 2 And 3 Should Have Been Excluded | Pension Benefits | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 169,400 169,400  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 169,400    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year   169,400  
Investments Classified As Level 2 And 3 Should Have Been Excluded | Pension Benefits | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 17,100 17,100  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 17,100    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year   17,100  
Investments Classified As Level 2 And 3 Should Have Been Excluded | Other Postretirement Benefits | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 57,100 57,100  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 57,100    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year   57,100  
Investments Classified As Level 2 And 3 Should Have Been Excluded | South Jersey Gas Company | Pension Benefits | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 136,600 136,600  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 136,600    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year   136,600  
Investments Classified As Level 2 And 3 Should Have Been Excluded | South Jersey Gas Company | Pension Benefits | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 13,700 13,700  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year 13,700    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year   13,700  
Investments Classified As Level 2 And 3 Should Have Been Excluded | South Jersey Gas Company | Other Postretirement Benefits | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 51,900 51,900  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Fair Value of Plan Assets at Beginning of Year $ 51,900    
Actual return on plan assets:      
Fair Value of Plan Assets at End of Year   $ 51,900