CONDENSED CONSOLIDATED BALANCE SHEETS (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Current Assets
Cash and cash equivalents	$ 8.1	$ 11.6	$ 0
Accounts receivable, net	129.8	123.9	132.3
Unbilled gas accounts receivable	42.7	75.4	62.5
Gas stored underground	13.0	40.3	11.3
Materials and supplies	31.9	25.7	21.2
Current regulatory assets	26.1	31.7	33.4
Prepaid expenses and other	6.4	10.7	6.5
Deferred income taxes - current	16.2	16.1	14.8
Total Current Assets	274.2	335.4	282.0
Property, plant and equipment	5,101.7	4,984.1	4,694.4
Accumulated depreciation, depletion and amortization	(1,926.6)	(1,885.7)	(1,796.6)
Net property, plant and equipment	3,175.1	3,098.4	2,897.8
Investment in unconsolidated affiliate	27.0	27.3	27.8
Noncurrent regulatory assets	20.1	21.0	20.6
Other noncurrent assets	43.4	50.7	39.3
TOTAL ASSETS	3,539.8	3,532.8	3,267.5
Current Liabilities
Checks outstanding in excess of cash balances	0	0	1.6
Short-term debt	129.0	219.0	86.0
Accounts payable and accrued expenses	180.4	242.9	165.1
Current regulatory liabilities	62.4	15.4	38.5
Current portion of long-term debt and capital lease obligation	132.4	91.5	182.0
Total Current Liabilities	504.2	568.8	473.2
Long-term debt and capital lease obligation, less current portion	992.2	993.0	898.5
Deferred income taxes	540.0	500.2	509.0
Asset retirement obligations	64.1	63.8	64.2
Defined benefit pension plan and other postretirement benefits	290.4	309.7	149.3
Customer contributions-in-aid-of-construction	26.2	26.6	45.7
Regulatory and other noncurrent liabilities	41.7	37.2	37.9
COMMON SHAREHOLDERS' EQUITY
Common stock	516.0	514.7	503.7
Retained earnings	791.1	744.9	690.0
Accumulated other comprehensive (loss)	(226.1)	(226.1)	(104.0)
Total Common Shareholders' Equity	1,081.0	1,033.5	1,089.7
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	3,539.8	3,532.8	3,267.5
Questar Gas [Member]
Current Assets
Cash and cash equivalents	4.5	5.0	0.4
Accounts receivable, net	86.1	77.6	95.9
Unbilled gas accounts receivable	42.6	75.2	62.4
Accounts receivable from affiliates	11.6	1.8	4.3
Gas stored underground	12.9	40.3	10.6
Materials and supplies	13.9	12.2	9.0
Current regulatory assets	20.8	26.5	32.9
Prepaid expenses and other	1.8	3.1	1.9
Deferred income taxes - current	5.6	5.6	4.3
Total Current Assets	199.8	247.3	221.7
Property, plant and equipment	1,958.5	1,927.0	1,833.5
Accumulated depreciation, depletion and amortization	(760.0)	(749.6)	(731.9)
Net property, plant and equipment	1,198.5	1,177.4	1,101.6
Noncurrent regulatory assets	14.7	15.1	14.4
Goodwill	5.6	5.6	5.6
Other noncurrent assets	2.4	2.3	2.5
TOTAL ASSETS	1,421.0	1,447.7	1,345.8
Current Liabilities
Notes payable to Questar	66.4	142.7	64.1
Accounts payable and accrued expenses	105.6	112.3	98.9
Accounts payable to affiliates	45.4	41.9	37.4
Customer advances	6.7	25.0	8.0
Current regulatory liabilities	60.9	14.2	35.3
Current portion of long-term debt and capital lease obligation	131.5	91.5	2.0
Total Current Liabilities	416.5	427.6	245.7
Long-term debt and capital lease obligation, less current portion	236.5	276.5	368.0
Deferred income taxes	257.8	259.8	239.3
Customer contributions-in-aid-of-construction	26.2	26.6	45.7
Regulatory and other noncurrent liabilities	4.7	4.8	5.5
COMMON SHAREHOLDERS' EQUITY
Common stock	23.0	23.0	23.0
Additional paid-in capital	171.7	171.4	150.6
Retained earnings	284.6	258.0	268.0
Total Common Shareholders' Equity	479.3	452.4	441.6
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	1,421.0	1,447.7	1,345.8
Questar Pipeline [Member]
Current Assets
Cash and cash equivalents	4.6	3.4	0.9
Notes receivable from Questar	14.5	8.8	40.7
Accounts receivable, net	19.3	19.1	25.5
Accounts receivable from affiliates	23.8	20.2	19.4
Materials and supplies	8.9	7.4	8.1
Prepaid expenses and other	8.4	9.6	3.9
Deferred income taxes - current	1.8	1.8	1.2
Total Current Assets	81.3	70.3	99.7
Property, plant and equipment	1,797.6	1,790.4	1,721.0
Accumulated depreciation, depletion and amortization	(599.6)	(586.7)	(557.4)
Net property, plant and equipment	1,198.0	1,203.7	1,163.6
Investment in unconsolidated affiliate	27.0	27.3	27.8
Goodwill	4.2	4.2	4.2
Regulatory and other noncurrent assets	9.5	10.1	9.1
TOTAL ASSETS	1,320.0	1,315.6	1,304.4
Current Liabilities
Accounts payable and accrued expenses	29.5	32.9	32.4
Accounts payable to affiliates	4.0	5.5	4.7
Current portion of long-term debt and capital lease obligation	0	0	180.0
Total Current Liabilities	33.5	38.4	217.1
Long-term debt and capital lease obligation, less current portion	458.9	459.0	280.9
Deferred income taxes	210.6	201.4	196.1
Regulatory and other noncurrent liabilities	13.5	14.7	15.4
COMMON SHAREHOLDERS' EQUITY
Common stock	6.6	6.6	6.6
Additional paid-in capital	346.2	345.7	344.5
Retained earnings	274.1	273.2	243.8
Accumulated other comprehensive (loss)	(23.4)	(23.4)	0
Total Common Shareholders' Equity	603.5	602.1	594.9
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	$ 1,320.0	$ 1,315.6	$ 1,304.4