Additional Statement Information [Abstract]

No definition available.

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- Definition

Value of stock issued during the period as a result of any share-based compensation plan.

+ References

No definition available.

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- Definition

Aggregate dividends declared during the period for each share of common stock outstanding.

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- Definition

Amount of paid and unpaid common stock dividends declared with the form of settlement in cash.

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	SJG	Common Stock	Common Stock SJG	Premium on Common Stock	Premium on Common Stock SJG	Treasury Stock	AOCL	AOCL SJG	Retained Earnings	Retained Earnings SJG
Beginning Balance at Dec. 31, 2018	$ 1,267,022	$ 1,008,022	$ 106,883	$ 5,848	$ 843,268	$ 355,744	$ (292)	$ (26,095)	$ (22,357)	$ 343,258	$ 668,787
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	85,637	68,731								85,637	68,731
Other Comprehensive Income, Net of Tax	8	8						8	8
Common Stock Issued or Granted Through Equity Offering or Stock Plans	188,449		8,603		179,829		17
Cash dividends	(26,562)									(26,562)
Ending Balance at Mar. 31, 2019	$ 1,514,554	$ 1,076,761	115,486	5,848	1,023,097	355,744	(275)	(26,087)	(22,349)	402,333	737,518
Additional Statement Information [Abstract]
Cash Dividends Declared (in dollars per share)	$ 0.29	$ 0
Beginning Balance at Dec. 31, 2019	$ 1,423,785	$ 1,089,898	115,493	5,848	1,027,902	355,744	(289)	(32,558)	(27,875)	313,237	756,181
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	101,041	70,522								101,041	70,522
Other Comprehensive Income, Net of Tax	8	8						8	8
Common Stock Issued or Granted Through Equity Offering or Stock Plans	(275)		62		(352)		15
Cash dividends	(27,276)									(27,276)
Ending Balance at Mar. 31, 2020	$ 1,497,283	$ 1,160,428	$ 115,555	$ 5,848	$ 1,027,550	$ 355,744	$ (274)	$ (32,550)	$ (27,867)	$ 387,002	$ 826,703
Additional Statement Information [Abstract]
Cash Dividends Declared (in dollars per share)	$ 0.30	$ 0