CONSOLIDATED STATEMENTS OF INCOME (Unaudited) (USD $) In Millions, except Per Share data	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
REVENUES
Questar Gas / Revenues from unaffiliated customers	$ 89.8	$ 89.8	$ 667.7	$ 599.1	$ 970.4	$ 891.5
Questar Pipeline / Revenues from unaffiliated customers	50.0	49.3	148.8	145.2	200.8	190.0
Wexpro	6.9	6.1	23.1	16.6	31.1	23.4
Total Revenues	146.7	145.2	839.6	760.9	1,202.3	1,104.9
OPERATING EXPENSES
Cost of sales (excluding operating expenses shown separately)	(30.0)	(23.2)	211.1	153.5	338.5	271.9
Operating and maintenance	35.4	36.8	126.6	127.9	174.5	181.4
General and administrative	24.1	27.2	83.3	78.4	113.4	102.0
Separation costs	0	0	0	11.5	0	11.5
Production and other taxes	13.5	11.9	40.2	39.7	51.1	49.3
Depreciation, depletion and amortization	40.1	38.2	118.4	114.5	157.3	153.3
Total Operating Expenses	83.1	90.9	579.6	525.5	834.8	769.4
Net gain (loss) from asset sales	0.2	0.1	0.3	0.1	0.6	(0.1)
OPERATING INCOME (LOSS)	63.8	54.4	260.3	235.5	368.1	335.4
Interest and other income	3.7	2.9	8.9	8.3	12.3	11.6
Income from unconsolidated affiliate	1.0	0.9	2.9	2.8	3.9	3.8
Interest expense	(13.3)	(14.1)	(44.1)	(42.4)	(58.8)	(56.8)
INCOME (LOSS) FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	55.2	44.1	228.0	204.2	325.5	294.0
Income taxes	(19.1)	(16.4)	(81.7)	(75.6)	(115.5)	(110.0)
INCOME (LOSS) FROM CONTINUING OPERATIONS	36.1	27.7	146.3	128.6	210.0	184.0
Discontinued operations, net of income taxes	0	0	0	148.2	0	243.7
Discontinued operations, noncontrolling interest	0	0	0	(1.3)	0	(2.2)
Total Discontinued Operations, Net Of Income Taxes	0	0	0	146.9	0	241.5
NET INCOME (LOSS) ATTRIBUTABLE TO QUESTAR	36.1	27.7	146.3	275.5	210.0	425.5
Earnings Per Common Share Attributable To Questar
Basic from continuing operations (in dollars per share)	$ 0.21	$ 0.15	$ 0.83	$ 0.73	$ 1.19	$ 1.04
Basic from discontinued operations (in dollars per share)	$ 0	$ 0	$ 0	$ 0.84	$ 0	$ 1.39
Basic total (in dollars per share)	$ 0.21	$ 0.15	$ 0.83	$ 1.57	$ 1.19	$ 2.43
Diluted from continuing operations (in dollars per share)	$ 0.20	$ 0.15	$ 0.82	$ 0.72	$ 1.17	$ 1.04
Diluted from discontinued operations (in dollars per share)	$ 0	$ 0	$ 0	$ 0.83	$ 0	$ 1.36
Diluted total (in dollars per share)	$ 0.20	$ 0.15	$ 0.82	$ 1.55	$ 1.17	$ 2.40
Weighted-average common shares outstanding
Used in basic calculation (in shares)	177.5	175.5	177.3	175.2	177.1	174.9
Used in diluted calculation (in shares)	178.9	178.2	178.7	177.7	178.8	177.3
Dividends per common share (in dollars per share)	$ 0.1525	$ 0.14	$ 0.4575	$ 0.40	$ 0.5975	$ 0.53
Questar Pipeline [Member]
REVENUES
Questar Pipeline / Revenues from unaffiliated customers	50.0	49.3	148.8	145.2	200.8	190.0
Revenues from affiliated companies	18.5	18.2	55.8	55.5	74.3	74.1
Total Revenues	68.5	67.5	204.6	200.7	275.1	264.1
OPERATING EXPENSES
Operating and maintenance	9.2	11.2	28.1	29.3	40.2	41.6
General and administrative	9.5	9.9	33.7	30.9	43.8	40.4
Depreciation and amortization	12.8	11.8	37.9	35.4	49.9	47.1
Other taxes	2.6	2.2	8.0	7.0	10.0	9.0
Cost of goods sold (excluding operating expenses shown separately)	0.7	0.6	2.3	1.6	3.1	1.8
Total Operating Expenses	34.8	35.7	110.0	104.2	147.0	139.9
Net gain (loss) from asset sales	0.2	0.1	0.3	0.2	0.9	0.3
OPERATING INCOME (LOSS)	33.9	31.9	94.9	96.7	129.0	124.5
Interest and other income	0.2	0	1.2	0.3	1.3	1.7
Income from unconsolidated affiliate	1.0	0.9	2.9	2.8	3.9	3.8
Interest expense	(5.6)	(7.1)	(19.5)	(21.8)	(26.5)	(29.1)
INCOME (LOSS) FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	29.5	25.7	79.5	78.0	107.7	100.9
Income taxes	(10.7)	(9.4)	(28.8)	(28.6)	(39.0)	(37.1)
NET INCOME (LOSS) ATTRIBUTABLE TO QUESTAR	18.8	16.3	50.7	49.4	68.7	63.8
Questar Gas [Member]
REVENUES
Questar Gas / Revenues from unaffiliated customers	89.8	89.8	667.7	599.1	970.4	891.5
Revenues from affiliated company	0.4	0.2	2.2	0.6	2.7	1.0
Total Revenues	90.2	90.0	669.9	599.7	973.1	892.5
OPERATING EXPENSES
Cost of natural gas sold (excluding operating expenses shown separately)	52.0	52.6	450.5	386.1	656.6	581.4
Operating and maintenance	20.8	20.9	82.6	84.4	112.6	120.7
General and administrative	10.1	12.5	34.9	35.3	49.5	46.8
Depreciation and amortization	11.1	10.8	32.9	33.1	43.5	44.2
Other taxes	4.1	3.5	12.4	11.4	15.1	13.5
Total Operating Expenses	98.1	100.3	613.3	550.3	877.3	806.6
OPERATING INCOME (LOSS)	(7.9)	(10.3)	56.6	49.4	95.8	85.9
Interest and other income	1.4	1.7	4.3	4.9	6.1	6.5
Interest expense	(6.4)	(6.2)	(19.5)	(19.5)	(26.2)	(26.3)
INCOME (LOSS) FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	(12.9)	(14.8)	41.4	34.8	75.7	66.1
Income taxes	5.0	5.7	(15.5)	(13.0)	(27.7)	(24.4)
NET INCOME (LOSS) ATTRIBUTABLE TO QUESTAR	$ (7.9)	$ (9.1)	$ 25.9	$ 21.8	$ 48.0	$ 41.7