CONSOLIDATED STATEMENTS OF INCOME (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
REVENUES
Questar Gas / Revenues from unaffiliated customers	$ 396.3	$ 418.3	$ 963.2	$ 912.0
Wexpro	12.3	10.3	47.1	37.2
Questar Pipeline / Revenues from unaffiliated customers	48.0	48.3	189.2	200.9
Other	0.3	0	0.5	0
Total Revenues	456.9	476.9	1,200.0	1,150.1
OPERATING EXPENSES
Cost of sales (excluding operating expenses shown separately)	148.2	199.7	234.4	239.3
Operating and maintenance	55.7	48.2	181.8	172.3
General and administrative	31.5	33.8	118.7	125.5
Retirement incentive	0	0	0	4.9
Production and other taxes	17.9	15.3	60.0	48.9
Depreciation, depletion and amortization	55.3	48.5	201.6	185.9
Asset impairment	0	0	80.6	0
Total Operating Expenses	308.6	345.5	877.1	776.8
Net gain (loss) from asset sales	0	0	(0.2)	2.9
OPERATING INCOME	148.3	131.4	322.7	376.2
Interest and other income	1.8	3.0	8.7	8.6
Income from unconsolidated affiliate	0.9	0.9	3.7	3.7
Interest expense	(15.8)	(14.5)	(58.2)	(57.7)
INCOME BEFORE INCOME TAXES	135.2	120.8	276.9	330.8
Income taxes	(50.1)	(47.9)	(103.5)	(121.1)
NET INCOME	85.1	72.9	173.4	209.7
Earnings Per Common Share
Basic	$ 0.48	$ 0.42	$ 0.98	$ 1.20
Diluted	$ 0.48	$ 0.41	$ 0.98	$ 1.19
Weighted-average common shares outstanding
Used in basic calculation	175.7	175.3	175.6	175.6
Used in diluted calculation	176.1	176.1	176.1	176.5
Dividends per common share	$ 0.18	$ 0.17	$ 0.72	$ 0.6725
Questar Gas [Member]
REVENUES
Questar Gas / Revenues from unaffiliated customers	396.3	418.3	963.2	912.0
Revenues from affiliated company	0	0.3	0.3	2.0
Total Revenues	396.3	418.6	963.5	914.0
OPERATING EXPENSES
Cost of natural gas sold (excluding operating expenses shown separately)	254.6	290.6	614.6	587.7
Operating and maintenance	39.8	33.7	119.2	111.8
General and administrative	13.8	12.7	53.6	52.2
Retirement incentive	0	0	0	2.4
Depreciation and amortization	13.2	12.1	50.8	47.5
Other taxes	5.1	5.2	17.9	17.0
Total Operating Expenses	326.5	354.3	856.1	818.6
OPERATING INCOME	69.8	64.3	107.4	95.4
Interest and other income	1.3	1.2	5.2	5.5
Interest expense	(7.1)	(5.8)	(23.6)	(23.1)
INCOME BEFORE INCOME TAXES	64.0	59.7	89.0	77.8
Income taxes	(24.4)	(22.7)	(33.6)	(28.6)
NET INCOME	39.6	37.0	55.4	49.2
Questar Pipeline [Member]
REVENUES
Questar Pipeline / Revenues from unaffiliated customers	48.0	48.3	189.2	200.9
Revenues from affiliated companies	19.3	19.5	76.5	75.4
Total Revenues	67.3	67.8	265.7	276.3
OPERATING EXPENSES
Operating and maintenance	8.1	7.4	33.2	34.0
General and administrative	11.5	12.4	45.8	50.3
Retirement incentive	0	0	0	0.9
Depreciation and amortization	13.6	14.1	55.0	54.9
Asset impairment	0	0	80.6	0
Other taxes	2.3	2.5	9.1	9.1
Cost of sales (excluding operating expenses shown separately)	1.7	1.2	6.6	7.4
Total Operating Expenses	37.2	37.6	230.3	156.6
Net gain (loss) from asset sales	0	0	0	2.7
OPERATING INCOME	30.1	30.2	35.4	122.4
Interest and other income	0.3	0.3	1.8	0.9
Income from unconsolidated affiliate	0.9	0.9	3.7	3.7
Interest expense	(6.5)	(6.5)	(25.8)	(26.2)
INCOME BEFORE INCOME TAXES	24.8	24.9	15.1	100.8
Income taxes	(9.1)	(9.1)	(7.0)	(36.9)
NET INCOME	$ 15.7	$ 15.8	$ 8.1	$ 63.9