CONSOLIDATED BALANCE SHEETS (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Current Assets
Cash and cash equivalents	$ 11.6	$ 21.8
Federal income taxes receivable	0	37.1
Accounts receivable, net	123.9	122.1
Unbilled gas accounts receivable	75.4	81.6
Inventories at lower of average cost or market:
Gas stored underground	40.3	43.7
Materials and supplies	25.7	19.0
Current regulatory assets	31.7	53.5
Prepaid expenses and other	10.7	9.0
Deferred income taxes - current	16.1	11.8
Total Current Assets	335.4	399.6
Property, Plant and Equipment
Distribution property, plant and equipment	1,927.0	1,817.6
Transportation property, plant and equipment	1,790.4	1,711.1
Cost-of-service gas and oil property, plant and equipment, successful efforts method	1,253.6	1,109.1
Other	13.1	5.0
Total property, plant and equipment	4,984.1	4,642.8
Distribution accumulated depreciation and amortization	(749.6)	(721.3)
Transportation accumulated depreciation and amortization	(586.7)	(545.0)
Cost-of-service gas and oil accumulated depreciation depletion and amortization	(545.0)	(487.8)
Other accumulated depreciation and amortization	(4.4)	(4.1)
Total accumulated depreciation, depletion and amortization	(1,885.7)	(1,758.2)
Total Property, Plant and Equipment, net	3,098.4	2,884.6
Investment in unconsolidated affiliate	27.3	27.9
Other Assets
Goodwill	9.8	9.8
Regulatory assets	21.0	21.7
Other noncurrent assets	40.9	30.0
Total Other Assets	71.7	61.5
TOTAL ASSETS	3,532.8	3,373.6
Current Liabilities
Short-term debt	219.0	242.0
Accounts payable and accrued expenses	175.7	160.5
Production and other taxes	31.5	29.9
Customer advances	25.0	26.2
Interest payable	10.7	8.5
Current regulatory liabilities	15.4	6.0
Current portion of long-term debt	91.5	182.0
Total Current Liabilities	568.8	655.1
Long-term debt, less current portion	993.0	898.5
Deferred income taxes	500.2	474.7
Asset retirement obligations	63.8	60.9
Defined benefit pension plan	255.0	130.0
Other postretirement benefits	54.7	39.5
Customer contributions-in-aid-of-construction	26.6	45.5
Regulatory and other noncurrent liabilities	37.2	33.3
Commitments and contingencies - Note 8
COMMON SHAREHOLDERS' EQUITY
Common stock	514.7	493.0
Retained earnings	744.9	647.1
Accumulated other comprehensive (loss)	(226.1)	(104.0)
Total Common Shareholders' Equity	1,033.5	1,036.1
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	3,532.8	3,373.6
Questar Pipeline [Member]
Current Assets
Cash and cash equivalents	3.4	5.3
Notes receivable from Questar	8.8	30.3
Federal income taxes receivable	0	1.1
Accounts receivable, net	19.1	19.1
Accounts receivable from affiliates	20.2	16.2
Inventories at lower of average cost or market:
Materials and supplies	7.4	7.2
Current regulatory assets	5.2	0.8
Prepaid expenses and other	9.6	5.2
Deferred income taxes - current	1.8	1.2
Total Current Assets	70.3	85.6
Property, Plant and Equipment
Transportation property, plant and equipment	1,358.5	1,196.8
Storage	287.8	281.8
Processing	25.4	25.3
General and intangible	65.3	63.4
Construction work in progress	53.4	143.8
Total property, plant and equipment	1,790.4	1,711.1
Total accumulated depreciation, depletion and amortization	(586.7)	(545.0)
Total Property, Plant and Equipment, net	1,203.7	1,166.1
Investment in unconsolidated affiliate	27.3	27.9
Other Assets
Goodwill	4.2	4.2
Regulatory assets	5.9	6.7
Regulatory and other noncurrent assets	10.1	9.6
Total Other Assets	14.3	13.8
TOTAL ASSETS	1,315.6	1,293.4
Current Liabilities
Accounts payable and accrued expenses	29.7	40.0
Accounts payable to affiliates	5.5	4.7
Interest payable	2.0	2.4
Current regulatory liabilities	1.2	3.2
Current portion of long-term debt	0	180.0
Total Current Liabilities	38.4	230.3
Long-term debt, less current portion	459.0	280.9
Deferred income taxes	201.4	180.1
Asset retirement obligations	2.8	4.1
Regulatory and other noncurrent liabilities	14.7	15.3
Commitments and contingencies - Note 8
COMMON SHAREHOLDERS' EQUITY
Common stock	6.6	6.6
Additional paid-in capital	345.7	344.0
Retained earnings	273.2	236.2
Accumulated other comprehensive (loss)	(23.4)	0
Total Common Shareholders' Equity	602.1	586.8
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	1,315.6	1,293.4
Questar Gas [Member]
Current Assets
Cash and cash equivalents	5.0	4.7
Federal income taxes receivable	1.5	7.7
Accounts receivable, net	76.1	85.3
Unbilled gas accounts receivable	75.2	81.5
Accounts receivable from affiliates	1.8	4.5
Inventories at lower of average cost or market:
Gas stored underground	40.3	43.3
Materials and supplies	12.2	7.9
Current regulatory assets	26.5	52.7
Prepaid expenses and other	3.1	2.9
Deferred income taxes - current	5.6	1.3
Total Current Assets	247.3	291.8
Property, Plant and Equipment
Distribution property, plant and equipment	1,583.1	1,490.1
Other	284.4	272.4
Construction work in progress	59.5	55.1
Total property, plant and equipment	1,927.0	1,817.6
Total accumulated depreciation, depletion and amortization	(749.6)	(721.3)
Total Property, Plant and Equipment, net	1,177.4	1,096.3
Other Assets
Goodwill	5.6	5.6
Regulatory assets	15.1	15.0
Other noncurrent assets	2.3	2.6
Total Other Assets	23.0	23.2
TOTAL ASSETS	1,447.7	1,411.3
Current Liabilities
Notes payable to Questar	142.7	153.6
Accounts payable and accrued expenses	106.5	102.5
Accounts payable to affiliates	41.9	53.6
Customer advances	25.0	26.2
Interest payable	5.8	5.8
Current regulatory liabilities	14.2	2.8
Current portion of long-term debt	91.5	2.0
Total Current Liabilities	427.6	346.5
Long-term debt, less current portion	276.5	368.0
Deferred income taxes	259.8	230.3
Asset retirement obligations	0.7	0.8
Customer contributions-in-aid-of-construction	26.6	45.5
Regulatory and other noncurrent liabilities	4.8	5.5
Commitments and contingencies - Note 8
COMMON SHAREHOLDERS' EQUITY
Common stock	23.0	23.0
Additional paid-in capital	171.4	150.3
Retained earnings	258.0	242.2
Total Common Shareholders' Equity	452.4	415.5
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	$ 1,447.7	$ 1,411.3