Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016	May 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Common stock, par value (in USD per share)	$ 1.25	$ 1.25	$ 1.25
Common stock, authorized (in shares)	120,000,000	120,000,000
Common stock, outstanding (in shares)	79,549,080	79,478,055		70,965,622	68,334,860
South Jersey Gas Company
Common stock, par value (in USD per share)	$ 2.50	$ 2.50
Common stock, authorized (in shares)	4,000,000	4,000,000
Common stock, outstanding (in shares)	2,339,139	2,339,139