Document And Entity Information (USD $) In Billions, except Share data	6 Months Ended
	Jun. 30, 2011	Jul. 31, 2011	Jun. 30, 2010
Entity Information [Line Items]
Entity Registrant Name	QUESTAR CORP
Entity Central Index Key	0000751652
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 7.8
Entity Common Stock, Shares Outstanding		177,507,911
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	Q2
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2011
Questar Pipeline [Member]
Entity Information [Line Items]
Entity Registrant Name	QUESTAR PIPELINE CO
Entity Central Index Key	0000764044
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		6,550,843
Questar Gas [Member]
Entity Information [Line Items]
Entity Registrant Name	QUESTAR GAS CO
Entity Central Index Key	0000068589
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		9,189,626