Document And Entity Information
 3 Months Ended
Mar. 31, 2015
Entity Information [Line Items]  
Entity Registrant Name QUESTAR CORP
Entity Central Index Key 0000751652
Current Fiscal Year End Date --12-31
Entity Filer Category Large Accelerated Filer
Document Type 10-Q
Document Period End Date Mar. 31, 2015
Document Fiscal Year Focus 2015
Document Fiscal Period Focus Q1
Amendment Flag false
Entity Common Stock, Shares Outstanding 175,712,882
Questar Gas [Member]  
Entity Information [Line Items]  
Entity Registrant Name QUESTAR GAS CO
Entity Central Index Key 0000068589
Current Fiscal Year End Date --12-31
Entity Filer Category Non-accelerated Filer
Document Type 10-Q
Document Period End Date Mar. 31, 2015
Document Fiscal Year Focus 2015
Document Fiscal Period Focus Q1
Amendment Flag false
Entity Common Stock, Shares Outstanding 9,189,626
Questar Pipeline [Member]  
Entity Information [Line Items]  
Entity Registrant Name QUESTAR PIPELINE CO
Entity Central Index Key 0000764044
Current Fiscal Year End Date --12-31
Entity Filer Category Non-accelerated Filer
Document Type 10-Q
Document Period End Date Mar. 31, 2015
Document Fiscal Year Focus 2015
Document Fiscal Period Focus Q1
Amendment Flag false
Entity Common Stock, Shares Outstanding 6,550,843