CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Common Stock, No Par Value	$ 0	$ 0
Common Stock, Shares Authorized	500,000,000	500,000,000
Common Stock, Shares Outstanding	175,000,000	175,400,000
Questar Gas [Member]
Common Stock, Par or Stated Value Per Share	$ 2.5	$ 2.5
Common Stock, Shares Authorized	50,000,000	50,000,000
Common Stock, Shares Issued	9,200,000	9,200,000
Common Stock, Shares Outstanding	9,200,000	9,200,000
Questar Pipeline [Member]
Common Stock, Par or Stated Value Per Share	$ 1	$ 1
Common Stock, Shares Authorized	25,000,000	25,000,000
Common Stock, Shares Issued	6,600,000	6,600,000
Common Stock, Shares Outstanding	6,600,000	6,600,000