PENSION AND OTHER POSTRETIREMENT BENEFITS - FAIR VALUE OF PLAN ASSETS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	$ 312,497	$ 312,497	$ 330,987
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	312,497	287,220
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	$ 330,987	312,497
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	$ 104,821	104,821	321,039
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	104,821
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	321,039	104,821
Pension Benefits | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	95,507	95,507	294,269
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	95,507
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	294,269	95,507
Pension Benefits | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	6,558	6,558	26,770
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	6,558
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	26,770	6,558
Pension Benefits | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	8,453	0
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	2,756	8,453
Actual return on plan assets:
Relating to assets still held at the reporting date	0	144
Relating to assets sold during the period	0	226
Purchases, Sales and Settlements	(2,756)	(6,067)
Fair Value of Plan Assets at End of Year	0	2,756
Pension Benefits | Measured at net asset value practical expedient:
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	46,226	46,226	9,948
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	46,226
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	9,948	46,226
Pension Benefits | Cash | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	2,493	2,493	881
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	2,493
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	881	2,493
Pension Benefits | Cash | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	2,493	2,493	881
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	2,493
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	881	2,493
Pension Benefits | Cash | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	0
Changes in significant unobservable inputs [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
Changes in significant unobservable inputs [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	1,702	1,702	5,779
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	1,702
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	5,779	1,702
Pension Benefits | STIF-Type Instrument | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	1,676	1,676	5,779
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	1,676
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	5,779	1,676
Pension Benefits | STIF-Type Instrument | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	26	26	0
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	26
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	0	26
Pension Benefits | STIF-Type Instrument | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	$ 0
Changes in significant unobservable inputs [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 (as a percent)			40.00%
Pension Benefits | U.S equity securities | Maximum
Actual return on plan assets:
Target plan allocation (as a percent)			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	30,863	30,863	$ 100,322
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	30,863
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	100,322	30,863
Pension Benefits | U.S. Large-Cap | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	30,863	30,863	100,322
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	30,863
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	100,322	30,863
Pension Benefits | U.S. Large-Cap | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	0
Changes in significant unobservable inputs [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
Changes in significant unobservable inputs [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	5,862	5,862	17,774
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	5,862
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	17,774	5,862
Pension Benefits | U.S. Mid-Cap | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	5,862	5,862	17,774
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	5,862
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	17,774	5,862
Pension Benefits | U.S. Mid-Cap | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	0
Changes in significant unobservable inputs [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
Changes in significant unobservable inputs [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. Small-Cap | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	3,958	3,958	14,938
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	3,958
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	14,938	3,958
Pension Benefits | U.S. Small-Cap | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	3,958	3,958	14,938
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	3,958
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	14,938	3,958
Pension Benefits | U.S. Small-Cap | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	0
Changes in significant unobservable inputs [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. Small-Cap | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	$ 0
Changes in significant unobservable inputs [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 | Minimum
Actual return on plan assets:
Target plan allocation (as a percent)			10.00%
Pension Benefits | International equity securities | Maximum
Actual return on plan assets:
Target plan allocation (as a percent)			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	33,523	33,523	$ 86,085
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	33,523
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	86,085	33,523
Pension Benefits | International equity securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	33,523	33,523	86,085
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	33,523
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	86,085	33,523
Pension Benefits | International equity securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	0
Changes in significant unobservable inputs [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
Changes in significant unobservable inputs [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 | Fixed income investments | Minimum
Actual return on plan assets:
Target plan allocation (as a percent)			25.00%
Pension Benefits | Fixed income investments | Maximum
Actual return on plan assets:
Target plan allocation (as a percent)			60.00%
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	2,756	2,756
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	2,756
Actual return on plan assets:
Fair Value of Plan Assets at End of Year		2,756
Pension Benefits | Guaranteed Insurance Contract | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Changes in significant unobservable inputs [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 | Guaranteed Insurance Contract | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Changes in significant unobservable inputs [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 | Guaranteed Insurance Contract | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	8,453	$ 0
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	2,756	8,453
Actual return on plan assets:
Relating to assets still held at the reporting date	0	144
Relating to assets sold during the period	0	226
Purchases, Sales and Settlements	(2,756)	(6,067)
Fair Value of Plan Assets at End of Year	0	2,756
Pension Benefits | Core Plus Fixed Income | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	23,664	23,664	54,066
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	23,664
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	54,066	23,664
Pension Benefits | Core Plus Fixed Income | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	17,132	17,132	27,296
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	17,132
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	27,296	17,132
Pension Benefits | Core Plus Fixed Income | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	6,532	6,532	26,770
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	6,532
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	26,770	6,532
Pension Benefits | Core Plus Fixed Income | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	$ 0
Changes in significant unobservable inputs [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 | Other investments | Minimum
Actual return on plan assets:
Target plan allocation (as a percent)			0.00%
Pension Benefits | Other investments | Maximum
Actual return on plan assets:
Target plan allocation (as a percent)			20.00%
Pension Benefits | Long Term Fixed | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	41,194	41,194
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	41,194
Actual return on plan assets:
Fair Value of Plan Assets at End of Year		41,194
Pension Benefits | Long Term Fixed | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	41,194	41,194
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	41,194
Actual return on plan assets:
Fair Value of Plan Assets at End of Year		41,194
Pension Benefits | Long Term Fixed | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Changes in significant unobservable inputs [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 | Long Term Fixed | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Changes in significant unobservable inputs [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 | Private Equity Funds and Common or Collective Trust Funds - Real Estate | Measured at net asset value practical expedient:
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	20,840	20,840
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	20,840
Actual return on plan assets:
Fair Value of Plan Assets at End of Year		20,840
Pension Benefits | Private Equity Funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	$ 0
Changes in significant unobservable inputs [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 | Measured at net asset value practical expedient:
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	9,650	9,650	9,948
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	9,650
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	9,948	9,650
Pension Benefits | Real Estate | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	0
Changes in significant unobservable inputs [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 | Measured at net asset value practical expedient:
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	11,190	11,190
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	11,190
Actual return on plan assets:
Fair Value of Plan Assets at End of Year		11,190
Pension Benefits | Other Common/Collective Trust Funds | Measured at net asset value practical expedient:
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	25,386	25,386
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	25,386
Actual return on plan assets:
Fair Value of Plan Assets at End of Year		25,386
Pension Benefits | Cash/Cash Equivalents | Measured at net asset value practical expedient:
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	23,965	23,965
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	23,965
Actual return on plan assets:
Fair Value of Plan Assets at End of Year		23,965
Pension Benefits | Equity Securities - U.S. | Measured at net asset value practical expedient:
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	1,421	1,421
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	1,421
Actual return on plan assets:
Fair Value of Plan Assets at End of Year		1,421
Pension Benefits | Pension Trust Receivables
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	161,450	161,450
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	161,450
Actual return on plan assets:
Fair Value of Plan Assets at End of Year		161,450
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	87,870	70,531	87,870
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	82,522	70,531
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	87,870	82,522
Other Postretirement Benefits | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	19,469	19,469	70,594
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	19,469
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	70,594	19,469
Other Postretirement Benefits | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	18,717	18,717	64,163
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	18,717
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	64,163	18,717
Other Postretirement Benefits | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	752	752	6,431
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	752
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	6,431	752
Other Postretirement Benefits | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	0
Changes in significant unobservable inputs [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 | Measured at net asset value practical expedient:
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	15,820	15,820	17,276
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	15,820
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	17,276	15,820
Other Postretirement Benefits | Cash | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	2,020	2,020	2,334
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	2,020
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	2,334	2,020
Other Postretirement Benefits | Cash | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	2,020	2,020	2,334
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	2,020
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	2,334	2,020
Other Postretirement Benefits | Cash | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	0
Changes in significant unobservable inputs [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 | Cash | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	$ 0
Changes in significant unobservable inputs [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 | U.S equity securities | Minimum
Actual return on plan assets:
Target plan allocation (as a percent)			55.00%
Other Postretirement Benefits | U.S equity securities | Maximum
Actual return on plan assets:
Target plan allocation (as a percent)			75.00%
Other Postretirement 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	5,585	5,585	$ 18,839
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	5,585
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	18,839	5,585
Other Postretirement Benefits | U.S. Large-Cap | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	5,585	5,585	18,839
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	5,585
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	18,839	5,585
Other Postretirement Benefits | U.S. Large-Cap | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	0
Changes in significant unobservable inputs [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 | U.S. Large-Cap | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	0
Changes in significant unobservable inputs [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 | U.S. Mid-Cap | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	1,038	1,038	4,379
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	1,038
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	4,379	1,038
Other Postretirement Benefits | U.S. Mid-Cap | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	1,038	1,038	4,379
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	1,038
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	4,379	1,038
Other Postretirement Benefits | U.S. Mid-Cap | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	0
Changes in significant unobservable inputs [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 | U.S. Mid-Cap | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	0
Changes in significant unobservable inputs [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 | U.S. Small-Cap | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	695	695	3,361
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	695
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	3,361	695
Other Postretirement Benefits | U.S. Small-Cap | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	695	695	3,361
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	695
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	3,361	695
Other Postretirement Benefits | U.S. Small-Cap | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	0
Changes in significant unobservable inputs [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 | U.S. Small-Cap | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	$ 0
Changes in significant unobservable inputs [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 | International equity securities | Minimum
Actual return on plan assets:
Target plan allocation (as a percent)			10.00%
Other Postretirement Benefits | International equity securities | Maximum
Actual return on plan assets:
Target plan allocation (as a percent)			20.00%
Other Postretirement Benefits | International equity securities | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	5,915	5,915	$ 20,369
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	5,915
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	20,369	5,915
Other Postretirement Benefits | International equity securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	5,915	5,915	20,369
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	5,915
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	20,369	5,915
Other Postretirement Benefits | International equity securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	0
Changes in significant unobservable inputs [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 | International equity securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	$ 0
Changes in significant unobservable inputs [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 | Fixed income investments | Minimum
Actual return on plan assets:
Target plan allocation (as a percent)			25.00%
Other Postretirement Benefits | Fixed income investments | Maximum
Actual return on plan assets:
Target plan allocation (as a percent)			45.00%
Other Postretirement Benefits | Core Plus Fixed Income | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	1,529	1,529	$ 6,431
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	1,529
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	6,431	1,529
Other Postretirement Benefits | Core Plus Fixed Income | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	777	777	0
Changes in significant unobservable inputs [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	0	777
Other Postretirement Benefits | Core Plus Fixed Income | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	752	752	6,431
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	752
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	6,431	752
Other Postretirement Benefits | Core Plus Fixed Income | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	0
Changes in significant unobservable inputs [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 - Bonds | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	2,588	2,588	14,881
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	2,588
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	14,881	2,588
Other Postretirement Benefits | Mutual Funds - Bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	2,588	2,588	14,881
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	2,588
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	14,881	2,588
Other Postretirement Benefits | Mutual Funds - Bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets			0
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	0
Other Postretirement Benefits | Mutual Funds - Bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets			$ 0
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	0
Other Postretirement Benefits | Other investments | Minimum
Actual return on plan assets:
Target plan allocation (as a percent)			0.00%
Other Postretirement Benefits | Other investments | Maximum
Actual return on plan assets:
Target plan allocation (as a percent)			7.00%
Other Postretirement Benefits | STIF Type Instrument | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	99	99
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	99
Actual return on plan assets:
Fair Value of Plan Assets at End of Year		99
Other Postretirement Benefits | STIF Type Instrument | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	99	99
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	99
Actual return on plan assets:
Fair Value of Plan Assets at End of Year		99
Other Postretirement Benefits | STIF Type Instrument | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year
Actual return on plan assets:
Fair Value of Plan Assets at End of Year
Other Postretirement Benefits | STIF Type Instrument | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year
Actual return on plan assets:
Fair Value of Plan Assets at End of Year
Other Postretirement Benefits | Company Owned Life Insurance | Measured at net asset value practical expedient:
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	15,820	15,820	$ 17,276
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	15,820
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	17,276	15,820
Other Postretirement Benefits | Pension Trust Receivables
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	47,233	47,233
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	47,233
Actual return on plan assets:
Fair Value of Plan Assets at End of Year		47,233
South Jersey Gas Company | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	170,959	170,959	181,940
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	170,959	160,285
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	181,940	170,959
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	3,719	3,719	174,002
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	3,719
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	174,002	3,719
South Jersey Gas Company | Pension Benefits | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	1,482	1,482	157,881
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	1,482
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	157,881	1,482
South Jersey Gas Company | Pension Benefits | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	21	21	16,121
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	21
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	16,121	21
South Jersey Gas Company | Pension Benefits | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	2,216	2,216	0
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	2,216	6,947
Actual return on plan assets:
Relating to assets still held at the reporting date	0	(34)
Relating to assets sold during the period	0	182
Purchases, Sales and Settlements	(2,216)	(4,879)
Fair Value of Plan Assets at End of Year	0	2,216
South Jersey Gas Company | Pension Benefits | Measured at net asset value practical expedient:
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	37,176	37,176	7,938
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	37,176
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	7,938	37,176
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	1,482	1,482	303
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	1,482
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	303	1,482
South Jersey Gas Company | Pension Benefits | Cash | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	1,482	1,482	303
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	1,482
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	303	1,482
South Jersey Gas Company | Pension Benefits | Cash | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	0
Changes in significant unobservable inputs [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
Changes in significant unobservable inputs [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	21	21	3,380
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	21
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	3,380	21
South Jersey Gas Company | Pension Benefits | STIF-Type Instrument | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	3,380
Changes in significant unobservable inputs [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	3,380	0
South Jersey Gas Company | Pension Benefits | STIF-Type Instrument | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	21	21	0
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	21
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	0	21
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
Changes in significant unobservable inputs [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	52,346		52,346
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	52,346
South Jersey Gas Company | Pension Benefits | U.S. Large-Cap | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	52,346		52,346
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	52,346
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
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	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
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	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	8,138		8,138
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	8,138
South Jersey Gas Company | Pension Benefits | U.S. Mid-Cap | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	8,138		8,138
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	8,138
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
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	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
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	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	8,249		8,249
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	8,249
South Jersey Gas Company | Pension Benefits | U.S. Small-Cap | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	8,249		8,249
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	8,249
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
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	0
South Jersey Gas Company | Pension Benefits | U.S. Small-Cap | 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 | International equity securities | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	44,120		44,120
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	44,120
South Jersey Gas Company | Pension Benefits | International equity securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	44,120		44,120
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	44,120
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	2,216	2,216
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	2,216
Actual return on plan assets:
Fair Value of Plan Assets at End of Year		2,216
South Jersey Gas Company | Pension Benefits | Guaranteed Insurance Contract | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Changes in significant unobservable inputs [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 | Guaranteed Insurance Contract | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0
Changes in significant unobservable inputs [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 | Guaranteed Insurance Contract | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	2,216	0
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	2,216	6,947
Actual return on plan assets:
Relating to assets still held at the reporting date	0	(34)
Relating to assets sold during the period	0	182
Purchases, Sales and Settlements	(2,216)	(4,879)
Fair Value of Plan Assets at End of Year	0	2,216
South Jersey Gas Company | Pension Benefits | Core Plus Fixed Income | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	32,571		32,571
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	32,571
South Jersey Gas Company | Pension Benefits | Core Plus Fixed Income | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	16,450		16,450
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	16,450
South Jersey Gas Company | Pension Benefits | Core Plus Fixed Income | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	16,121		16,121
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	16,121
South Jersey Gas Company | Pension Benefits | Core Plus Fixed Income | 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 | Long Term Fixed | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	24,895		24,895
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	24,895
South Jersey Gas Company | Pension Benefits | Long Term Fixed | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	24,895		24,895
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	24,895
South Jersey Gas Company | Pension Benefits | Long Term Fixed | 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 | Long Term Fixed | 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 | Private Equity Funds and Common or Collective Trust Funds - Real Estate | Measured at net asset value practical expedient:
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	16,760	16,760
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	16,760
Actual return on plan assets:
Fair Value of Plan Assets at End of Year		16,760
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
Changes in significant unobservable inputs [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 | Measured at net asset value practical expedient:
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	7,761	7,761	7,938
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	7,761
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	7,938	7,761
South Jersey Gas Company | Pension Benefits | Real Estate | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	0
Changes in significant unobservable inputs [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 | Measured at net asset value practical expedient:
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	8,999	8,999
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	8,999
Actual return on plan assets:
Fair Value of Plan Assets at End of Year		8,999
South Jersey Gas Company | Pension Benefits | Other Common/Collective Trust Funds | Measured at net asset value practical expedient:
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	20,416	20,416
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	20,416
Actual return on plan assets:
Fair Value of Plan Assets at End of Year		20,416
South Jersey Gas Company | Pension Benefits | Cash/Cash Equivalents | Measured at net asset value practical expedient:
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	19,273	19,273
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	19,273
Actual return on plan assets:
Fair Value of Plan Assets at End of Year		19,273
South Jersey Gas Company | Pension Benefits | Equity Securities - U.S. | Measured at net asset value practical expedient:
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	1,143	1,143
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	1,143
Actual return on plan assets:
Fair Value of Plan Assets at End of Year		1,143
South Jersey Gas Company | Pension Benefits | Pension Trust Receivables
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	130,064	130,064
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	130,064
Actual return on plan assets:
Fair Value of Plan Assets at End of Year		130,064
South Jersey Gas Company | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	59,190	59,190	61,869
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	59,190	49,770
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	61,869	59,190
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	1,895	1,895	45,660
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	1,895
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	45,660	1,895
South Jersey Gas Company | Other Postretirement Benefits | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	1,895	1,895	40,919
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	1,895
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	40,919	1,895
South Jersey Gas Company | Other Postretirement Benefits | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	4,741
Changes in significant unobservable inputs [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	4,741	0
South Jersey Gas Company | Other Postretirement Benefits | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	0
Changes in significant unobservable inputs [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 | Measured at net asset value practical expedient:
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	14,843	14,843	16,209
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	14,843
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	16,209	14,843
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	1,895	1,895	2,083
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	1,895
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	2,083	1,895
South Jersey Gas Company | Other Postretirement Benefits | Cash | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	1,895	1,895	2,083
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	1,895
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	2,083	1,895
South Jersey Gas Company | Other Postretirement Benefits | Cash | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	0
Changes in significant unobservable inputs [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 | Cash | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	0	0	0
Changes in significant unobservable inputs [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 | U.S. Large-Cap | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	10,764		10,764
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	10,764
South Jersey Gas Company | Other Postretirement Benefits | U.S. Large-Cap | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	10,764		10,764
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	10,764
South Jersey Gas Company | Other Postretirement Benefits | U.S. Large-Cap | 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 | U.S. Large-Cap | 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 | U.S. Mid-Cap | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	2,591		2,591
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	2,591
South Jersey Gas Company | Other Postretirement Benefits | U.S. Mid-Cap | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	2,591		2,591
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	2,591
South Jersey Gas Company | Other Postretirement Benefits | U.S. Mid-Cap | 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 | U.S. Mid-Cap | 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 | U.S. Small-Cap | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	2,200		2,200
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	2,200
South Jersey Gas Company | Other Postretirement Benefits | U.S. Small-Cap | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	2,200		2,200
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	2,200
South Jersey Gas Company | Other Postretirement Benefits | U.S. Small-Cap | 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 | U.S. Small-Cap | 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 | International equity securities | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	12,889		12,889
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	12,889
South Jersey Gas Company | Other Postretirement Benefits | International equity securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	12,889		12,889
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	12,889
South Jersey Gas Company | Other Postretirement 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 | Other Postretirement 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 | Other Postretirement Benefits | Core Plus Fixed Income | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	4,741		4,741
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	4,741
South Jersey Gas Company | Other Postretirement Benefits | Core Plus Fixed Income | Level 1
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 | Core Plus Fixed Income | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	4,741		4,741
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	4,741
South Jersey Gas Company | Other Postretirement Benefits | Core Plus Fixed Income | 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 - Bonds | Fair Value, Inputs, Level 1, 2 and 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	10,392		10,392
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	10,392
South Jersey Gas Company | Other Postretirement Benefits | Mutual Funds - Bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	10,392		10,392
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	10,392
South Jersey Gas Company | Other Postretirement Benefits | Mutual Funds - Bonds | 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 | Mutual Funds - Bonds | 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 | Company Owned Life Insurance | Measured at net asset value practical expedient:
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	14,843	14,843	$ 16,209
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	14,843
Actual return on plan assets:
Fair Value of Plan Assets at End of Year	16,209	14,843
South Jersey Gas Company | Other Postretirement Benefits | Pension Trust Receivables
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	42,452	42,452
Changes in significant unobservable inputs [Roll forward]
Fair Value of Plan Assets at Beginning of Year	$ 42,452
Actual return on plan assets:
Fair Value of Plan Assets at End of Year		$ 42,452