STOCK-BASED COMPENSATION PLAN (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2017
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of options granted (in shares)			0	0
Number of options outstanding (in shares)		0		0		0
Vesting period of shares					3 years
Service period of shares			3 years
Fair value per share (in dollars per share)	$ 28.53		$ 24.96			$ 28.53
Expected volatility, measurement period			3 years
Total Cost	$ 1,373	$ 1,025	$ 2,699	$ 2,035
Capitalized	(104)	(106)	(192)	(212)
Net Expense	$ 1,269	919	$ 2,507	1,823
Unrecognized compensation cost of awards granted under the plan						$ 7,900
Weighted average period over which unrecognized compensation cost is to be recognized			2 years
Additional disclosures [Abstract]
Weighted average fair value nonvested shares-beginning balance (in dollars per share)			$ 24.96
Weighted average fair value nonvested shares-granted during the period (in dollars per share)			33.24
Weighted average fair value nonvested shares-vested during the period (in dollars per share)			24.75
Weighted average fair value nonvested shares-ending balance (in dollars per share)	$ 28.53		$ 28.53
South Jersey Gas Company
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Costs capitalized			50.00%
Officers and Key Employees
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of shares granted (in shares)			167,444
Shares outstanding (in shares)	432,318		295,515			432,318
Total Cost	$ 1,117	798	$ 2,187	$ 1,615
Number of shares awarded			65,628	13,247
Fair value of shares issued			$ 2,200	$ 300
Restricted stock award activity, excluding accrued dividend equivalents [Roll Forward]
Nonvested shares outstanding, beginning balance (in shares)			295,515
Granted (in shares)			167,444
Vested (in shares)			(30,641)
Nonvested shares outstanding, ending balance (in shares)	432,318		432,318
Officers and Key Employees | 2015 - TSR
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares outstanding (in shares)	33,537		33,537			33,537
Fair value per share (in dollars per share)	$ 26.31		$ 26.31			$ 26.31
Expected volatility			16.00%
Risk-free interest rate			1.10%
Restricted stock award activity, excluding accrued dividend equivalents [Roll Forward]
Nonvested shares outstanding, ending balance (in shares)	33,537		33,537
Additional disclosures [Abstract]
Weighted average fair value nonvested shares-ending balance (in dollars per share)	$ 26.31		$ 26.31
Officers and Key Employees | 2015 - EGR, ROE, Time
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares outstanding (in shares)	61,586		61,586			61,586
Fair value per share (in dollars per share)	$ 29.47		$ 29.47			$ 29.47
Restricted stock award activity, excluding accrued dividend equivalents [Roll Forward]
Nonvested shares outstanding, ending balance (in shares)	61,586		61,586
Additional disclosures [Abstract]
Weighted average fair value nonvested shares-ending balance (in dollars per share)	$ 29.47		$ 29.47
Officers and Key Employees | 2016 - TSR
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares outstanding (in shares)	66,101		66,101			66,101
Fair value per share (in dollars per share)	$ 22.53		$ 22.53			$ 22.53
Expected volatility			18.10%
Risk-free interest rate			1.31%
Restricted stock award activity, excluding accrued dividend equivalents [Roll Forward]
Nonvested shares outstanding, ending balance (in shares)	66,101		66,101
Additional disclosures [Abstract]
Weighted average fair value nonvested shares-ending balance (in dollars per share)	$ 22.53		$ 22.53
Officers and Key Employees | 2016 - CEGR, Time
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares outstanding (in shares)	103,650		103,650			103,650
Fair value per share (in dollars per share)	$ 23.52		$ 23.52			$ 23.52
Restricted stock award activity, excluding accrued dividend equivalents [Roll Forward]
Nonvested shares outstanding, ending balance (in shares)	103,650		103,650
Additional disclosures [Abstract]
Weighted average fair value nonvested shares-ending balance (in dollars per share)	$ 23.52		$ 23.52
Officers and Key Employees | 2017 - TSR
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares outstanding (in shares)	57,237		57,237			57,237
Fair value per share (in dollars per share)	$ 32.17		$ 32.17			$ 32.17
Expected volatility			20.80%
Risk-free interest rate			1.47%
Restricted stock award activity, excluding accrued dividend equivalents [Roll Forward]
Nonvested shares outstanding, ending balance (in shares)	57,237		57,237
Additional disclosures [Abstract]
Weighted average fair value nonvested shares-ending balance (in dollars per share)	$ 32.17		$ 32.17
Officers and Key Employees | 2017 - CEGR, Time
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares outstanding (in shares)	110,207		110,207			110,207
Fair value per share (in dollars per share)	$ 33.69		$ 33.69			$ 33.69
Restricted stock award activity, excluding accrued dividend equivalents [Roll Forward]
Nonvested shares outstanding, ending balance (in shares)	110,207		110,207
Additional disclosures [Abstract]
Weighted average fair value nonvested shares-ending balance (in dollars per share)	$ 33.69		$ 33.69
Director
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of shares granted (in shares)			30,394	35,197
Vesting period of shares			12 months
Director shares vested						100.00%
Shares outstanding (in shares)	30,394		35,197			30,394
Total Cost	$ 256	$ 227	$ 512	$ 420
Fair value of shares issued			$ 1,000	$ 800
Restricted stock award activity, excluding accrued dividend equivalents [Roll Forward]
Nonvested shares outstanding, beginning balance (in shares)			35,197
Granted (in shares)			30,394	35,197
Vested (in shares)			(35,197)
Nonvested shares outstanding, ending balance (in shares)	30,394		30,394
Director | 2017
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Shares outstanding (in shares)	30,394		30,394			30,394
Fair value per share (in dollars per share)	$ 33.64		$ 33.64			$ 33.64
Restricted stock award activity, excluding accrued dividend equivalents [Roll Forward]
Nonvested shares outstanding, ending balance (in shares)	30,394		30,394
Additional disclosures [Abstract]
Weighted average fair value nonvested shares-ending balance (in dollars per share)	$ 33.64		$ 33.64
Stock Appreciation Rights
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of shares granted (in shares)			0
Restricted stock award activity, excluding accrued dividend equivalents [Roll Forward]
Granted (in shares)			0
Restricted Stock | Year two
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Service period of shares					2 years
Restricted Stock | Year three
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Service period of shares					3 years
Restricted Stock | Officers and Key Employees
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of shares granted (in shares)			167,444	193,184
Restricted stock award activity, excluding accrued dividend equivalents [Roll Forward]
Granted (in shares)			167,444	193,184
Restricted Stock | Officers and Key Employees | Minimum
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Percentage of actual amount of shares that ultimately vest of original share units granted			0.00%
Restricted Stock | Officers and Key Employees | Maximum
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Percentage of actual amount of shares that ultimately vest of original share units granted			200.00%
Restricted Stock | South Jersey Gas Company's officers and other key employees
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of shares granted (in shares)			24,001	32,732
Net Expense			$ 300	$ 200
Restricted stock award activity, excluding accrued dividend equivalents [Roll Forward]
Granted (in shares)			24,001	32,732
Time-based Restricted Stock
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Return on equity award threshold					7.00%
Time-based Restricted Stock | Officers and Key Employees
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of shares granted (in shares)			52,971	57,955
Vesting period of shares			3 years		3 years
Payout limit					100.00%
Restricted stock award activity, excluding accrued dividend equivalents [Roll Forward]
Granted (in shares)			52,971	57,955
Total Shareholder Return
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Vesting period of shares			3 years