CONDENSED CONSOLIDATED BALANCE SHEETS (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011
Current Assets
Cash and cash equivalents	$ 0	$ 11.6	$ 0
Accounts receivable, net	73.1	123.9	85.1
Unbilled gas accounts receivable	12.4	75.4	15.0
Gas stored underground	29.8	40.3	18.7
Materials and supplies	29.5	25.7	21.5
Current regulatory assets	25.2	31.7	33.2
Prepaid expenses and other	9.7	10.7	9.0
Deferred income taxes - current	16.2	16.1	14.8
Total Current Assets	195.9	335.4	197.3
Property, plant and equipment	5,170.1	4,984.1	4,759.8
Accumulated depreciation, depletion and amortization	(1,959.3)	(1,885.7)	(1,825.5)
Net property, plant and equipment	3,210.8	3,098.4	2,934.3
Investment in unconsolidated affiliate	27.1	27.3	27.4
Noncurrent regulatory assets	20.1	21.0	20.5
Other noncurrent assets	43.5	50.7	41.9
TOTAL ASSETS	3,497.4	3,532.8	3,221.4
Current Liabilities
Checks outstanding in excess of cash balances	11.8	0	4.5
Short-term debt	190.0	219.0	137.0
Accounts payable and accrued expenses	164.5	242.9	136.0
Current regulatory liabilities	5.1	15.4	24.8
Current portion of long-term debt and capital lease obligation	132.2	91.5	82.0
Total Current Liabilities	503.6	568.8	384.3
Long-term debt and capital lease obligation, less current portion	991.6	993.0	901.8
Deferred income taxes	561.0	500.2	536.5
Asset retirement obligations	65.6	63.8	65.2
Defined benefit pension plan and other postretirement benefits	266.2	309.7	149.5
Customer contributions-in-aid-of-construction	28.1	26.6	45.8
Regulatory and other noncurrent liabilities	37.5	37.2	32.2
COMMON SHAREHOLDERS' EQUITY
Common stock	468.3	514.7	506.4
Retained earnings	801.5	744.9	703.2
Accumulated other comprehensive income (loss)	(226.0)	(226.1)	(103.5)
Total Common Shareholders' Equity	1,043.8	1,033.5	1,106.1
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	3,497.4	3,532.8	3,221.4
Questar Gas [Member]
Current Assets
Cash and cash equivalents	0	5.0	0
Accounts receivable, net	28.4	77.6	50.3
Unbilled gas accounts receivable	12.3	75.2	14.7
Accounts receivable from affiliates	22.7	1.8	1.8
Gas stored underground	29.4	40.3	18.7
Materials and supplies	12.9	12.2	10.3
Current regulatory assets	18.5	26.5	33.1
Prepaid expenses and other	4.0	3.1	3.3
Deferred income taxes - current	5.6	5.6	4.3
Total Current Assets	133.8	247.3	136.5
Property, plant and equipment	1,990.7	1,927.0	1,856.1
Accumulated depreciation, depletion and amortization	(763.8)	(749.6)	(734.9)
Net property, plant and equipment	1,226.9	1,177.4	1,121.2
Noncurrent regulatory assets	15.1	15.1	14.8
Goodwill	5.6	5.6	5.6
Other noncurrent assets	2.1	2.3	2.4
TOTAL ASSETS	1,383.5	1,447.7	1,280.5
Current Liabilities
Checks outstanding in excess of cash balances	5.4	0	2.9
Notes payable to Questar	102.1	142.7	44.0
Accounts payable and accrued expenses	78.8	112.3	56.7
Accounts payable to affiliates	43.6	41.9	36.2
Customer advances	19.9	25.0	9.7
Current regulatory liabilities	3.4	14.2	21.3
Current portion of long-term debt and capital lease obligation	131.5	91.5	2.0
Total Current Liabilities	384.7	427.6	172.8
Long-term debt and capital lease obligation, less current portion	236.5	276.5	368.0
Deferred income taxes	260.6	259.8	253.7
Customer contributions-in-aid-of-construction	28.1	26.6	45.8
Regulatory and other noncurrent liabilities	4.5	4.8	5.5
COMMON SHAREHOLDERS' EQUITY
Common stock	23.0	23.0	23.0
Additional paid-in capital	172.0	171.4	150.9
Retained earnings	274.1	258.0	260.8
Total Common Shareholders' Equity	469.1	452.4	434.7
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	1,383.5	1,447.7	1,280.5
Questar Pipeline [Member]
Current Assets
Cash and cash equivalents	0.3	3.4	0.2
Notes receivable from Questar	18.8	8.8	0
Accounts receivable, net	18.9	19.1	19.2
Accounts receivable from affiliates	27.9	20.2	19.6
Materials and supplies	9.0	7.4	7.0
Current regulatory assets	6.7	5.2	0.1
Prepaid expenses and other	3.7	4.4	4.0
Deferred income taxes - current	1.8	1.8	1.2
Total Current Assets	87.1	70.3	51.3
Property, plant and equipment	1,804.6	1,790.4	1,739.4
Accumulated depreciation, depletion and amortization	(609.2)	(586.7)	(569.2)
Net property, plant and equipment	1,195.4	1,203.7	1,170.2
Investment in unconsolidated affiliate	27.1	27.3	27.4
Goodwill	4.2	4.2	4.2
Regulatory and other noncurrent assets	8.9	10.1	8.3
TOTAL ASSETS	1,322.7	1,315.6	1,261.4
Current Liabilities
Notes payable to Questar	0	0	49.3
Accounts payable and accrued expenses	40.0	31.7	25.7
Accounts payable to affiliates	4.0	5.5	2.8
Current regulatory liabilities	1.7	1.2	3.5
Current portion of long-term debt and capital lease obligation	0	0	80.0
Total Current Liabilities	45.7	38.4	161.3
Long-term debt and capital lease obligation, less current portion	459.0	459.0	281.0
Deferred income taxes	200.2	201.4	198.8
Regulatory and other noncurrent liabilities	13.5	14.7	15.6
COMMON SHAREHOLDERS' EQUITY
Common stock	6.6	6.6	6.6
Additional paid-in capital	346.6	345.7	344.9
Retained earnings	274.4	273.2	252.7
Accumulated other comprehensive income (loss)	(23.3)	(23.4)	0.5
Total Common Shareholders' Equity	604.3	602.1	604.7
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	$ 1,322.7	$ 1,315.6	$ 1,261.4