CONDENSED CONSOLIDATED BALANCE SHEETS (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Current Assets
Cash and cash equivalents	$ 4.8	$ 32.0	$ 5.6
Accounts receivable, net	104.5	118.1	130.6
Unbilled gas accounts receivable	41.5	93.7	56.3
Gas stored underground	12.4	43.7	6.9
Materials and supplies	28.7	30.4	25.0
Current regulatory assets	43.0	79.6	29.8
Prepaid expenses and other	8.7	11.2	7.5
Deferred income taxes - current	8.2	5.8	14.5
Total Current Assets	251.8	414.5	276.2
Property, Plant and Equipment	6,033.1	5,961.5	5,723.5
Accumulated depreciation, depletion and amortization	(2,277.2)	(2,226.0)	(2,121.6)
Net Property, Plant and Equipment	3,755.9	3,735.5	3,601.9
Investment in unconsolidated affiliate	24.5	24.7	25.2
Noncurrent regulatory assets	23.6	25.0	19.3
Other noncurrent assets	50.1	50.0	51.8
TOTAL ASSETS	4,105.9	4,249.7	3,974.4
Current Liabilities
Short-term debt	214.0	347.0	157.0
Accounts payable and accrued expenses	200.5	234.9	229.9
Current regulatory liabilities	5.2	13.4	17.2
Current portion of long-term debt and capital lease obligation	277.8	26.1	0.9
Total Current Liabilities	697.5	621.4	405.0
Long-term debt and capital lease obligation, less current portion	1,005.1	1,257.5	1,284.7
Deferred income taxes	716.6	715.6	712.6
Asset retirement obligations	75.0	69.3	68.6
Defined benefit pension plan and other postretirement benefits	155.7	185.7	108.5
Noncurrent regulatory liabilities	72.5	69.9	63.2
Customer contributions in aid of construction	28.0	29.2	32.0
Other noncurrent liabilities	57.2	54.9	43.6
COMMON SHAREHOLDERS' EQUITY
Common stock	477.6	476.8	465.7
Retained earnings	1,018.2	970.7	929.6
Accumulated other comprehensive (loss)	(197.5)	(201.3)	(139.1)
Total Common Shareholders' Equity	1,298.3	1,246.2	1,256.2
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	4,105.9	4,249.7	3,974.4
Questar Gas [Member]
Current Assets
Cash and cash equivalents	0	19.8	1.4
Notes receivable from Questar	0	0	30.6
Accounts receivable, net	81.2	66.4	102.6
Unbilled gas accounts receivable	41.5	93.7	56.3
Accounts receivable from affiliates	56.3	45.2	31.3
Gas stored underground	9.5	40.3	6.2
Materials and supplies	17.3	19.2	13.2
Current regulatory assets	42.1	78.3	24.0
Prepaid expenses and other	2.4	3.5	2.4
Deferred income taxes - current	0	0	2.9
Total Current Assets	250.3	366.4	270.9
Property, Plant and Equipment	2,400.7	2,352.3	2,230.0
Accumulated depreciation, depletion and amortization	(791.5)	(780.3)	(754.3)
Net Property, Plant and Equipment	1,609.2	1,572.0	1,475.7
Noncurrent regulatory assets	20.3	21.3	15.4
Other noncurrent assets	9.2	9.3	9.5
TOTAL ASSETS	1,889.0	1,969.0	1,771.5
Current Liabilities
Checks outstanding in excess of cash balances	0.4	0	0
Notes payable to Questar	35.8	119.3	0
Accounts payable and accrued expenses	126.0	111.9	111.3
Accounts payable to affiliates	71.4	78.7	65.6
Dividends payable to Questar	0	9.0	0
Customer advances	9.5	29.4	7.2
Current regulatory liabilities	4.3	12.5	15.2
Deferred income taxes - current	3.9	6.3	0
Total Current Liabilities	251.3	367.1	199.3
Long-term debt and capital lease obligation, less current portion	534.5	534.5	534.5
Deferred income taxes	377.5	377.5	340.6
Noncurrent regulatory liabilities	63.3	60.9	54.8
Customer contributions in aid of construction	28.0	29.2	32.0
Other noncurrent liabilities	2.8	2.8	3.1
COMMON SHAREHOLDERS' EQUITY
Common stock	23.0	23.0	23.0
Additional paid-in capital	265.7	265.4	264.2
Retained earnings	342.9	308.6	320.0
Total Common Shareholders' Equity	631.6	597.0	607.2
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	1,889.0	1,969.0	1,771.5
Questar Pipeline [Member]
Current Assets
Cash and cash equivalents	6.1	7.4	4.9
Notes receivable from Questar	35.9	40.1	46.6
Accounts receivable, net	16.8	17.9	17.5
Accounts receivable from affiliates	44.3	39.2	33.8
Gas stored underground	2.9	3.4	0.7
Materials and supplies	7.1	6.9	7.5
Current regulatory assets	0.9	1.3	5.8
Prepaid expenses and other	3.6	4.3	2.8
Deferred income taxes - current	1.9	1.9	1.8
Total Current Assets	119.5	122.4	121.4
Property, Plant and Equipment	1,837.5	1,827.7	1,782.8
Accumulated depreciation, depletion and amortization	(687.9)	(673.9)	(640.6)
Net Property, Plant and Equipment	1,149.6	1,153.8	1,142.2
Investment in unconsolidated affiliate	24.5	24.7	25.2
Noncurrent regulatory and other assets	10.4	10.8	11.3
TOTAL ASSETS	1,304.0	1,311.7	1,300.1
Current Liabilities
Accounts payable and accrued expenses	33.9	21.7	38.7
Accounts payable to affiliates	3.4	5.8	3.4
Dividends payable to Questar	0	16.0	0
Current regulatory liabilities	0.9	0.9	2.0
Current portion of long-term debt and capital lease obligation	25.1	25.1	0
Total Current Liabilities	63.3	69.5	44.1
Long-term debt and capital lease obligation, less current portion	433.7	433.7	458.8
Deferred income taxes	241.3	241.4	228.6
Noncurrent regulatory and other liabilities	16.0	15.9	15.9
COMMON SHAREHOLDERS' EQUITY
Common stock	6.6	6.6	6.6
Additional paid-in capital	351.9	351.4	350.1
Retained earnings	213.6	215.7	218.8
Accumulated other comprehensive (loss)	(22.4)	(22.5)	(22.8)
Total Common Shareholders' Equity	549.7	551.2	552.7
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	$ 1,304.0	$ 1,311.7	$ 1,300.1