CONDENSED CONSOLIDATED BALANCE SHEETS (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Current Assets
Cash and cash equivalents	$ 5.6	$ 16.0	$ 7.2
Accounts receivable, net	130.6	123.8	141.2
Unbilled gas accounts receivable	56.3	93.4	50.5
Gas stored underground	6.9	40.0	9.8
Materials and supplies	25.0	23.7	30.0
Current regulatory assets	29.8	35.8	31.3
Prepaid expenses and other	7.5	9.5	6.8
Deferred income taxes - current	14.5	9.7	17.2
Total Current Assets	276.2	351.9	294.0
Property, Plant and Equipment	5,723.5	5,674.7	5,399.4
Accumulated depreciation, depletion and amortization	(2,121.6)	(2,071.7)	(2,011.0)
Net Property, Plant and Equipment	3,601.9	3,603.0	3,388.4
Investment in unconsolidated affiliate	25.2	25.6	26.1
Noncurrent regulatory assets	19.3	20.5	20.4
Other noncurrent assets	51.8	53.3	47.8
TOTAL ASSETS	3,974.4	4,054.3	3,776.7
Current Liabilities
Short-term debt	157.0	276.0	202.0
Accounts payable and accrued expenses	229.9	264.8	222.8
Current regulatory liabilities	17.2	14.1	36.8
Current portion of long-term debt and capital lease obligation	0.9	0.9	2.8
Total Current Liabilities	405.0	555.8	464.4
Long-term debt and capital lease obligation, less current portion	1,284.7	1,285.5	1,137.6
Deferred income taxes	712.6	707.2	636.1
Asset retirement obligations	68.6	67.7	61.2
Defined benefit pension plan and other postretirement benefits	108.5	113.2	271.3
Noncurrent regulatory liabilities	63.2	61.2	56.5
Customer contributions in aid of construction	32.0	29.1	23.8
Other noncurrent liabilities	43.6	35.8	39.7
COMMON SHAREHOLDERS' EQUITY
Common stock	465.7	464.5	444.8
Retained earnings	929.6	876.1	882.6
Accumulated other comprehensive (loss)	(139.1)	(141.8)	(241.3)
Total Common Shareholders' Equity	1,256.2	1,198.8	1,086.1
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	3,974.4	4,054.3	3,776.7
Questar Gas [Member]
Current Assets
Cash and cash equivalents	1.4	8.8	2.8
Notes receivable from Questar	30.6	0	0
Accounts receivable, net	102.6	88.9	103.7
Unbilled gas accounts receivable	56.3	93.4	50.4
Accounts receivable from affiliates	31.3	30.4	32.8
Gas stored underground	6.2	39.2	9.6
Materials and supplies	13.2	12.1	14.4
Current regulatory assets	24.0	30.2	26.1
Prepaid expenses and other	2.4	3.0	2.2
Deferred income taxes - current	2.9	2.9	5.7
Total Current Assets	270.9	308.9	247.7
Property, Plant and Equipment	2,230.0	2,203.0	2,062.8
Accumulated depreciation, depletion and amortization	(754.3)	(745.2)	(724.0)
Net Property, Plant and Equipment	1,475.7	1,457.8	1,338.8
Noncurrent regulatory assets	15.4	16.1	15.7
Goodwill	5.6	5.6	5.6
Other noncurrent assets	3.9	4.0	3.1
TOTAL ASSETS	1,771.5	1,792.4	1,610.9
Current Liabilities
Notes payable to Questar	0	17.7	132.3
Accounts payable and accrued expenses	111.3	139.2	109.9
Accounts payable to affiliates	65.6	67.8	51.1
Customer advances	7.2	19.8	7.2
Current regulatory liabilities	15.2	11.1	35.6
Current portion of long-term debt and capital lease obligation	0	0	2.0
Total Current Liabilities	199.3	255.6	338.1
Long-term debt and capital lease obligation, less current portion	534.5	534.5	384.5
Deferred income taxes	340.6	340.7	316.5
Noncurrent regulatory liabilities	54.8	53.0	48.6
Customer contributions in aid of construction	32.0	29.1	23.8
Other noncurrent liabilities	3.1	3.2	3.3
COMMON SHAREHOLDERS' EQUITY
Common stock	23.0	23.0	23.0
Additional paid-in capital	264.2	263.9	172.9
Retained earnings	320.0	289.4	300.2
Total Common Shareholders' Equity	607.2	576.3	496.1
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	1,771.5	1,792.4	1,610.9
Questar Pipeline [Member]
Current Assets
Cash and cash equivalents	4.9	2.7	5.4
Notes receivable from Questar	46.6	29.4	33.1
Accounts receivable, net	17.5	18.5	18.6
Accounts receivable from affiliates	33.8	36.6	34.0
Materials and supplies	8.2	8.1	10.9
Current regulatory assets	5.8	5.6	5.2
Prepaid expenses and other	2.8	4.4	3.3
Deferred income taxes - current	1.8	1.8	1.6
Total Current Assets	121.4	107.1	112.1
Property, Plant and Equipment	1,782.8	1,774.3	1,852.7
Accumulated depreciation, depletion and amortization	(640.6)	(627.2)	(642.7)
Net Property, Plant and Equipment	1,142.2	1,147.1	1,210.0
Investment in unconsolidated affiliate	25.2	25.6	26.1
Goodwill	4.2	4.2	4.2
Noncurrent regulatory and other assets	7.1	7.7	8.7
TOTAL ASSETS	1,300.1	1,291.7	1,361.1
Current Liabilities
Accounts payable and accrued expenses	38.7	25.6	31.5
Accounts payable to affiliates	3.4	9.4	3.4
Current regulatory liabilities	2.0	3.0	1.2
Total Current Liabilities	44.1	38.0	36.1
Long-term debt and capital lease obligation, less current portion	458.8	458.9	458.9
Deferred income taxes	228.6	228.6	245.8
Noncurrent regulatory and other liabilities	15.9	13.9	14.0
COMMON SHAREHOLDERS' EQUITY
Common stock	6.6	6.6	6.6
Additional paid-in capital	350.1	349.5	348.1
Retained earnings	218.8	219.1	274.7
Accumulated other comprehensive (loss)	(22.8)	(22.9)	(23.1)
Total Common Shareholders' Equity	552.7	552.3	606.3
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	$ 1,300.1	$ 1,291.7	$ 1,361.1