CONSOLIDATED STATEMENTS OF INCOME (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
REVENUES
Questar Gas / Revenues from unaffiliated customers	$ 100.7	$ 89.4	$ 642.0	$ 647.8	$ 979.4	$ 928.8
Wexpro	9.4	13.2	29.5	32.0	42.6	41.0
Questar Pipeline / Revenues from unaffiliated customers	47.3	47.0	143.4	142.3	190.6	195.3
Other	0.5	0	1.2	0	1.4	0
Total Revenues	157.9	149.6	816.1	822.1	1,214.0	1,165.1
OPERATING EXPENSES
Cost of sales (excluding operating expenses shown separately)	(42.3)	(35.0)	81.6	157.4	210.1	250.6
Operating and maintenance	39.2	36.4	136.1	122.2	188.2	169.8
General and administrative	26.0	24.4	88.0	90.2	118.8	123.0
Retirement incentive	0	0	0	0	0	4.9
Production and other taxes	16.8	15.2	53.4	45.2	65.6	55.1
Depreciation, depletion and amortization	50.8	47.4	162.9	143.4	214.3	189.4
Abandonment and impairment	0	80.6	2.0	80.6	2.0	80.6
Total Operating Expenses	90.5	169.0	524.0	639.0	799.0	873.4
Net gain (loss) from asset sales	1.5	0	1.6	0.1	1.3	0.1
OPERATING INCOME (LOSS)	68.9	(19.4)	293.7	183.2	416.3	291.8
Interest and other income	2.0	3.1	5.0	9.2	5.7	10.5
Income from unconsolidated affiliate	0.9	0.9	2.7	2.8	3.6	3.7
Interest expense	(15.7)	(13.9)	(47.3)	(42.7)	(61.5)	(56.3)
INCOME (LOSS) BEFORE INCOME TAXES	56.1	(29.3)	254.1	152.5	364.1	249.7
Income taxes	(17.5)	10.1	(90.1)	(59.4)	(132.0)	(92.8)
NET INCOME (LOSS)	38.6	(19.2)	164.0	93.1	232.1	156.9
Earnings (Loss) Per Common Share
Basic	$ 0.22	$ (0.11)	$ 0.93	$ 0.53	$ 1.32	$ 0.89
Diluted	$ 0.22	$ (0.11)	$ 0.93	$ 0.53	$ 1.32	$ 0.89
Weighted-average common shares outstanding
Used in basic calculation	175.8	175.5	175.8	175.4	175.7	175.5
Used in diluted calculation	176.1	175.5	176.1	176.1	176.0	176.1
Dividends per common share	$ 0.19	$ 0.18	$ 0.56	$ 0.53	$ 0.74	$ 0.70
Questar Gas [Member]
REVENUES
Questar Gas / Revenues from unaffiliated customers	100.7	89.4	642.0	647.8	979.4	928.8
Revenues from affiliated company	0	0.2	0	0.6	0	0.8
Total Revenues	100.7	89.6	642.0	648.4	979.4	929.6
OPERATING EXPENSES
Cost of natural gas sold (excluding operating expenses shown separately)	56.8	50.1	398.6	424.2	625.0	601.1
Operating and maintenance	22.7	20.9	88.8	78.1	123.8	109.9
General and administrative	12.3	12.1	39.0	38.5	53.0	53.2
Retirement incentive	0	0	0	0	0	2.4
Depreciation and amortization	13.5	12.4	40.3	36.9	53.1	49.1
Other taxes	4.8	5.3	14.7	15.4	17.3	18.3
Total Operating Expenses	110.1	100.8	581.4	593.1	872.2	834.0
Net gain (loss) from asset sales	0	0	0.1	0	0.1	0
OPERATING INCOME (LOSS)	(9.4)	(11.2)	60.7	55.3	107.3	95.6
Interest and other income	1.7	1.3	4.3	3.8	5.6	5.5
Interest expense	(7.1)	(5.3)	(21.2)	(16.7)	(26.8)	(21.7)
INCOME (LOSS) BEFORE INCOME TAXES	(14.8)	(15.2)	43.8	42.4	86.1	79.4
Income taxes	5.7	6.2	(16.6)	(15.6)	(32.9)	(28.8)
NET INCOME (LOSS)	(9.1)	(9.0)	27.2	26.8	53.2	50.6
Questar Pipeline [Member]
REVENUES
Questar Pipeline / Revenues from unaffiliated customers	47.3	47.0	143.4	142.3	190.6	195.3
Revenues from affiliated companies	17.7	17.6	54.7	54.8	76.6	74.0
Total Revenues	65.0	64.6	198.1	197.1	267.2	269.3
OPERATING EXPENSES
Operating and maintenance	9.5	8.8	25.5	23.2	34.8	32.0
General and administrative	10.2	10.8	32.5	35.3	43.9	48.8
Retirement incentive	0	0	0	0	0	0.9
Depreciation and amortization	13.5	14.0	40.7	42.2	54.0	55.9
Abandonment and impairment	0	80.6	0	80.6	0	80.6
Other taxes	2.4	2.5	7.1	7.4	9.0	9.2
Cost of sales (excluding operating expenses shown separately)	0.6	0.5	3.0	2.7	6.4	7.5
Total Operating Expenses	36.2	117.2	108.8	191.4	148.1	234.9
Net gain (loss) from asset sales	0	0	0	0	0	0.1
OPERATING INCOME (LOSS)	28.8	(52.6)	89.3	5.7	119.1	34.5
Interest and other income	0.3	0.6	0.7	1.2	1.3	1.5
Income from unconsolidated affiliate	0.9	0.9	2.7	2.8	3.6	3.7
Interest expense	(6.5)	(6.5)	(19.6)	(19.5)	(25.9)	(26.0)
INCOME (LOSS) BEFORE INCOME TAXES	23.5	(57.6)	73.1	(9.8)	98.1	13.7
Income taxes	(8.6)	19.7	(26.8)	2.2	(36.0)	(6.4)
NET INCOME (LOSS)	$ 14.9	$ (37.9)	$ 46.3	$ (7.6)	$ 62.1	$ 7.3