CONSOLIDATED BALANCE SHEETS (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Current Assets
Cash and cash equivalents	$ 32.0	$ 16.0
Accounts receivable, net	89.6	119.3
Unbilled gas accounts receivable	93.7	93.4
Federal income taxes receivable	28.5	4.5
Inventories, at lower of average cost or market:
Gas stored underground	43.7	40.0
Materials and supplies	30.4	23.7
Current regulatory assets	79.6	35.8
Prepaid expenses and other	11.2	9.5
Deferred income taxes - current	5.8	9.7
Total Current Assets	414.5	351.9
Property, Plant and Equipment
Distribution property, plant and equipment	2,352.3	2,203.0
Cost-of-service gas and oil property, plant and equipment, successful efforts method	1,688.4	1,626.4
Transportation property, plant and equipment	1,827.7	1,774.3
Other property, plant and equipment	93.1	71.0
Total Property, Plant and Equipment	5,961.5	5,674.7
Distribution accumulated depreciation and amortization	(780.3)	(745.2)
Cost-of-service gas and oil accumulated depreciation, depletion and amortization	(757.3)	(689.8)
Transportation accumulated depreciation and amortization	(673.9)	(627.2)
Other accumulated depreciation and amortization	(14.5)	(9.5)
Total accumulated depreciation, depletion and amortization	(2,226.0)	(2,071.7)
Net Property, Plant and Equipment	3,735.5	3,603.0
Investment in unconsolidated affiliate	24.7	25.6
Other Assets
Goodwill	9.8	9.8
Noncurrent regulatory assets	25.0	20.5
Other noncurrent assets	40.2	43.5
Total Other Assets	75.0	73.8
TOTAL ASSETS	4,249.7	4,054.3
Current Liabilities
Short-term debt	347.0	276.0
Accounts payable	116.0	158.0
Accrued expenses and other	42.3	42.1
Production and other taxes	35.5	34.7
Customer advances	29.4	19.8
Current regulatory liabilities	13.4	14.1
Interest payable	11.7	10.2
Current portion of long-term debt	25.1	0
Current portion of capital lease obligation	1.0	0.9
Total Current Liabilities	621.4	555.8
Long-term debt, less current portion	1,220.1	1,247.1
Capital lease obligation, less current portion	37.4	38.4
Deferred income taxes	715.6	707.2
Asset retirement obligations	69.3	67.7
Defined benefit pension plan	141.9	70.7
Other postretirement benefits	43.8	42.5
Noncurrent regulatory liabilities	69.9	61.2
Customer contributions in aid of construction	29.2	29.1
Other noncurrent liabilities	54.9	35.8
Commitments and contingencies - Note 9
COMMON SHAREHOLDERS' EQUITY
Common stock	476.8	464.5
Retained earnings	970.7	876.1
Accumulated other comprehensive loss	(201.3)	(141.8)
Total Common Shareholders' Equity	1,246.2	1,198.8
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	4,249.7	4,054.3
Questar Gas [Member]
Current Assets
Cash and cash equivalents	19.8	8.8
Accounts receivable, net	66.4	86.1
Unbilled gas accounts receivable	93.7	93.4
Accounts receivable from affiliates	45.2	30.4
Federal income taxes receivable	0	2.8
Inventories, at lower of average cost or market:
Gas stored underground	40.3	39.2
Materials and supplies	19.2	12.1
Current regulatory assets	78.3	30.2
Prepaid expenses and other	3.5	3.0
Deferred income taxes - current	0	2.9
Total Current Assets	366.4	308.9
Property, Plant and Equipment
Distribution property, plant and equipment	1,991.6	1,839.8
Other property, plant and equipment	306.3	289.8
Construction work in progress	54.4	73.4
Total Property, Plant and Equipment	2,352.3	2,203.0
Total accumulated depreciation, depletion and amortization	(780.3)	(745.2)
Net Property, Plant and Equipment	1,572.0	1,457.8
Other Assets
Goodwill	5.6	5.6
Noncurrent regulatory assets	21.3	16.1
Other noncurrent assets	3.7	4.0
Total Other Assets	30.6	25.7
TOTAL ASSETS	1,969.0	1,792.4
Current Liabilities
Notes payable to Questar	119.3	17.7
Accounts payable	76.0	110.8
Accounts payable to affiliates	78.7	67.8
Accrued expenses and other	22.7	23.2
Dividends payable to Questar	9.0	0
Customer advances	29.4	19.8
Federal income taxes payable	6.4	0
Current regulatory liabilities	12.5	11.1
Interest payable	6.8	5.2
Deferred income taxes - current	6.3	0
Total Current Liabilities	367.1	255.6
Long-term debt, less current portion	534.5	534.5
Deferred income taxes	377.5	340.7
Asset retirement obligations	0.6	0.6
Noncurrent regulatory liabilities	60.9	53.0
Customer contributions in aid of construction	29.2	29.1
Other noncurrent liabilities	2.8	3.2
Commitments and contingencies - Note 9
COMMON SHAREHOLDERS' EQUITY
Common stock	23.0	23.0
Additional paid-in capital	265.4	263.9
Retained earnings	308.6	289.4
Total Common Shareholders' Equity	597.0	576.3
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	1,969.0	1,792.4
Questar Pipeline [Member]
Current Assets
Cash and cash equivalents	7.4	2.7
Notes receivable from Questar	40.1	29.4
Accounts receivable, net	17.2	18.5
Accounts receivable from affiliates	39.2	36.6
Federal income taxes receivable	0.7	0
Inventories, at lower of average cost or market:
Materials and supplies	10.3	8.1
Current regulatory assets	1.3	5.6
Prepaid expenses and other	4.3	4.4
Deferred income taxes - current	1.9	1.8
Total Current Assets	122.4	107.1
Property, Plant and Equipment
Transportation property, plant and equipment	1,371.6	1,331.0
Other property, plant and equipment	82.7	82.1
Storage	300.3	296.2
Processing	24.9	24.1
Construction work in progress	48.2	40.9
Total Property, Plant and Equipment	1,827.7	1,774.3
Total accumulated depreciation, depletion and amortization	(673.9)	(627.2)
Net Property, Plant and Equipment	1,153.8	1,147.1
Investment in unconsolidated affiliate	24.7	25.6
Other Assets
Goodwill	4.2	4.2
Noncurrent regulatory assets	3.7	4.4
Noncurrent regulatory and other assets	6.6	7.7
Total Other Assets	10.8	11.9
TOTAL ASSETS	1,311.7	1,291.7
Current Liabilities
Accounts payable	9.7	7.5
Accounts payable to affiliates	5.8	9.4
Accrued expenses and other	9.9	13.1
Dividends payable to Questar	16.0	0
Federal income taxes payable	0	2.9
Current regulatory liabilities	0.9	3.0
Interest payable	2.1	2.1
Current portion of long-term debt	25.1	0
Total Current Liabilities	69.5	38.0
Long-term debt, less current portion	433.7	458.9
Deferred income taxes	241.4	228.6
Asset retirement obligations	2.3	2.2
Noncurrent regulatory liabilities	9.0	8.2
Noncurrent regulatory and other liabilities	15.9	13.9
Commitments and contingencies - Note 9
COMMON SHAREHOLDERS' EQUITY
Common stock	6.6	6.6
Additional paid-in capital	351.4	349.5
Retained earnings	215.7	219.1
Accumulated other comprehensive loss	(22.5)	(22.9)
Total Common Shareholders' Equity	551.2	552.3
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	$ 1,311.7	$ 1,291.7