CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Common Stock, No Par Value	$ 0
Common Stock, Shares Authorized	500,000,000
Common Stock, Shares Outstanding	175,000,000	177,900,000
Questar Gas [Member]
Common Stock, Par or Stated Value Per Share	$ 0
Common Stock, Shares Authorized	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	$ 0
Common Stock, Shares Authorized	25,000,000
Common Stock, Shares Issued	6,600,000	6,600,000
Common Stock, Shares Outstanding	6,600,000	6,600,000