CONSOLIDATED STATEMENTS OF INCOME (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
REVENUES
Questar Gas / Revenues from unaffiliated customers	$ 960.9	$ 985.2	$ 859.7
Wexpro	35.6	45.1	36.1
Questar Pipeline / Revenues from unaffiliated customers	190.2	189.5	203.1
Other	2.6	0.2	0
Total Revenues	1,189.3	1,220.0	1,098.9
OPERATING EXPENSES
Cost of sales (excluding operating expenses shown separately)	186.3	285.9	192.3
Cost of natural gas sold
Operating and maintenance	189.0	174.3	180.8
General and administrative	127.9	121.0	120.8
Retirement incentive	0	0	4.9
Production and other taxes	66.2	57.4	47.9
Depreciation, depletion and amortization	213.7	194.8	181.6
Abandonment and impairment	2.0	80.6	0
Total Operating Expenses	785.1	914.0	728.3
Net gain (loss) from asset sales	1.2	(0.2)	5.1
OPERATING INCOME	405.4	305.8	375.7
Interest and other income	6.6	9.9	7.0
Income from unconsolidated affiliate	3.5	3.7	3.7
Interest expense	(63.1)	(56.9)	(57.9)
INCOME BEFORE INCOME TAXES	352.4	262.5	328.5
Income taxes	(125.9)	(101.3)	(116.5)
NET INCOME	226.5	161.2	212.0
Earnings Per Common Share
Basic	$ 1.29	$ 0.92	$ 1.20
Diluted	$ 1.29	$ 0.92	$ 1.19
Weighted-average common shares outstanding
Used in basic calculation	175.8	175.4	176.5
Used in diluted calculation	176.1	176.0	177.5
Questar Gas [Member]
REVENUES
Questar Gas / Revenues from unaffiliated customers	960.9	985.2	859.7
Revenues from affiliated company	0	0.6	2.5
Total Revenues	960.9	985.8	862.2
Cost of natural gas sold
Cost of natural gas sold - unaffiliated parties	181.4	279.7	185.6
Cost of natural gas sold - affiliated companies	423.4	370.9	347.7
Total cost of natural gas sold (excluding operating expenses shown separately) / Total Questar Gas cost of natural gas sold	604.8	650.6	533.3
Operating and maintenance	122.5	113.1	119.0
General and administrative	52.8	52.5	51.2
Retirement incentive	0	0	2.4
Depreciation and amortization	53.6	49.7	47.2
Other taxes	17.8	18.0	16.2
Total Operating Expenses	851.5	883.9	769.3
Net gain (loss) from asset sales	0.1	0	0
OPERATING INCOME	109.5	101.9	92.9
Interest and other income	5.9	5.1	5.5
Interest expense	(28.2)	(22.3)	(24.1)
INCOME BEFORE INCOME TAXES	87.2	84.7	74.3
Income taxes	(32.0)	(31.9)	(27.2)
NET INCOME	55.2	52.8	47.1
Questar Pipeline [Member]
REVENUES
Questar Pipeline / Revenues from unaffiliated customers	190.2	189.5	203.1
Revenues from affiliated companies	73.7	76.7	74.4
Total Revenues	263.9	266.2	277.5
Cost of natural gas sold
Operating and maintenance	34.1	32.5	35.2
General and administrative	44.1	46.7	50.0
Retirement incentive	0	0	0.9
Depreciation and amortization	54.5	55.5	54.3
Abandonment and impairment	0	80.6	0
Other taxes	9.1	9.3	9.1
Cost of sales (excluding operating expenses shown separately)	4.0	6.1	6.7
Total Operating Expenses	145.8	230.7	156.2
Net gain (loss) from asset sales	(0.5)	0	2.7
OPERATING INCOME	117.6	35.5	124.0
Interest and other income	1.2	1.8	0.6
Income from unconsolidated affiliate	3.5	3.7	3.7
Interest expense	(26.1)	(25.8)	(26.3)
INCOME BEFORE INCOME TAXES	96.2	15.2	102.0
Income taxes	(35.6)	(7.0)	(37.3)
NET INCOME	$ 60.6	$ 8.2	$ 64.7