CONSOLIDATED STATEMENTS OF INCOME (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012	Mar. 31, 2011
REVENUES
Questar Gas / Revenues from unaffiliated customers	$ 366.0	$ 413.9	$ 917.6	$ 955.0
Wexpro	9.2	7.8	32.9	26.2
Questar Pipeline / Revenues from unaffiliated customers	50.5	48.3	199.6	197.8
Total Revenues	425.7	470.0	1,150.1	1,179.0
OPERATING EXPENSES
Cost of sales (excluding operating expenses shown separately)	152.7	209.9	264.3	332.5
Operating and maintenance	56.7	51.4	181.2	175.4
General and administrative	29.1	33.0	114.0	115.3
Separation costs	0	0	0	11.5
Production and other taxes	14.3	13.6	53.2	49.6
Depreciation, depletion and amortization	44.2	39.4	164.7	153.9
Total Operating Expenses	297.0	347.3	777.4	838.2
Net gain (loss) from asset sales	2.2	0.1	2.3	0.5
OPERATING INCOME	130.9	122.8	375.0	341.3
Interest and other income	1.4	2.9	8.9	11.8
Income from unconsolidated affiliate	0.9	0.9	3.8	3.7
Interest expense	(14.7)	(16.0)	(55.5)	(58.8)
Income From Continuing Operations Before Income Taxes	118.5	110.6	332.2	298.0
Income taxes	(43.3)	(40.7)	(119.0)	(108.0)
Income from Continuing Operations	75.2	69.9	213.2	190.0
Discontinued operations, net of income taxes	0	0	0	69.5
Discontinued operations, noncontrolling interest	0	0	0	(0.7)
Total Discontinued Operations, Net Of Income Taxes	0	0	0	68.8
NET INCOME ATTRIBUTABLE TO QUESTAR	75.2	69.9	213.2	258.8
Earnings Per Common Share Attributable To Questar
Basic from continuing operations	$ 0.42	$ 0.40	$ 1.19	$ 1.08
Basic from discontinued operations	$ 0.00	$ 0.00	$ 0.00	$ 0.39
Basic total	$ 0.42	$ 0.40	$ 1.19	$ 1.47
Diluted from continuing operations	$ 0.42	$ 0.39	$ 1.19	$ 1.06
Diluted from discontinued operations	$ 0.00	$ 0.00	$ 0.00	$ 0.39
Diluted total	$ 0.42	$ 0.39	$ 1.19	$ 1.45
Weighted-average common shares outstanding
Used in basic calculation	178.2	177.0	177.8	176.2
Used in diluted calculation	179.3	178.5	179.1	178.5
Dividends per common share (in dollars per share)	$ 0.1625	$ 0.1525	$ 0.63	$ 0.5625
Questar Gas [Member]
REVENUES
Questar Gas / Revenues from unaffiliated customers	366.0	413.9	917.6	955.0
Revenues from affiliated company	0.8	0.8	3.3	1.6
Total Revenues	366.8	414.7	920.9	956.6
OPERATING EXPENSES
Cost of natural gas sold (excluding operating expenses shown separately)	236.2	288.7	593.2	643.9
Operating and maintenance	40.9	37.4	122.0	112.8
General and administrative	11.7	14.6	48.1	53.2
Depreciation and amortization	11.8	10.9	45.4	43.5
Other taxes	4.4	4.3	15.1	14.4
Total Operating Expenses	305.0	355.9	823.8	867.8
OPERATING INCOME	61.8	58.8	97.1	88.8
Interest and other income	1.2	1.6	5.0	6.8
Interest expense	(6.8)	(6.6)	(26.1)	(26.0)
Income From Continuing Operations Before Income Taxes	56.2	53.8	76.0	69.6
Income taxes	(21.3)	(20.4)	(28.4)	(25.4)
NET INCOME ATTRIBUTABLE TO QUESTAR	34.9	33.4	47.6	44.2
Questar Pipeline [Member]
REVENUES
Questar Pipeline / Revenues from unaffiliated customers	50.5	48.3	199.6	197.8
Revenues from affiliated companies	18.5	18.6	74.3	73.8
Total Revenues	69.0	66.9	273.9	271.6
OPERATING EXPENSES
Operating and maintenance	8.6	8.6	35.3	42.2
General and administrative	12.1	13.1	45.5	43.5
Depreciation and amortization	13.5	12.3	52.4	47.9
Other taxes	2.5	3.1	9.5	9.7
Cost of goods sold (excluding operating expenses shown separately)	0.5	0.6	3.0	2.5
Total Operating Expenses	37.2	37.7	145.7	145.8
Net gain (loss) from asset sales	0	0.1	0.2	0.8
OPERATING INCOME	31.8	29.3	128.4	126.6
Interest and other income	0	0.9	0	1.2
Income from unconsolidated affiliate	0.9	0.9	3.8	3.7
Interest expense	(6.6)	(7.1)	(24.0)	(28.5)
Income From Continuing Operations Before Income Taxes	26.1	24.0	108.2	103.0
Income taxes	(9.5)	(8.7)	(39.0)	(37.5)
NET INCOME ATTRIBUTABLE TO QUESTAR	$ 16.6	$ 15.3	$ 69.2	$ 65.5