CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (USD $) In Millions	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010
OPERATING ACTIVITIES
Net income	$ 110.2	$ 249.1
Discontinued operations, net of income taxes	0	(148.2)
Adjustments to reconcile net income to net cash provided by operating activities from continuing operations:
Depreciation, depletion and amortization	83.1	80.0
Deferred income taxes	58.5	9.1
Share-based compensation	5.9	9.6
Net (gain) from asset sales	(0.1)	0
(Income) from unconsolidated affiliate	(1.9)	(1.9)
Distribution from unconsolidated affiliate	2.4	1.8
Gain on interest rate swap	(0.7)	0
Changes in operating assets and liabilities	112.0	56.2
Net Cash Provided By Operating Activities From Continuing Operations	369.4	255.7
INVESTING ACTIVITIES
Property, plant and equipment	(143.4)	(139.5)
Equity investment in QEP	0	(250.0)
Cash used in disposition of assets	(1.1)	(1.0)
Proceeds from disposition of assets	0.2	0.5
Change in notes receivable	0	39.3
Net Cash Used In Investing Activities By Continuing Operations	(144.3)	(350.7)
FINANCING ACTIVITIES
Common stock issued	5.6	9.3
Common stock repurchased	(2.6)	(8.4)
Change in short-term debt	(105.0)	176.0
Change in notes payable	0	(52.9)
Long-term debt repaid	(100.0)	0
Long-term debt issuance costs	0	(2.9)
Checks outstanding in excess of cash balances	4.5	5.8
Dividends paid	(54.1)	(45.5)
Tax benefits from share-based compensation	4.7	2.1
Net Cash Provided By (Used In) Financing Activities By Continuing Operations	(246.9)	83.5
CASH USED IN CONTINUING OPERATIONS	(21.8)	(11.5)
Cash provided by operating activities of discontinued operations	0	468.2
Cash used in investing activities of discontinued operations	0	(598.6)
Cash provided by financing activities of discontinued operations	0	111.1
Effect of change in cash and cash equivalents of discontinued operations	0	19.3
Change in cash and cash equivalents	(21.8)	(11.5)
Beginning cash and cash equivalents	21.8	11.5
Ending cash and cash equivalents	0	0
Questar Pipeline [Member]
OPERATING ACTIVITIES
Net income	31.9	33.1
Adjustments to reconcile net income to net cash provided by operating activities from continuing operations:
Depreciation and amortization	26.6	24.9
Deferred income taxes	18.4	3.1
Share-based compensation	0.9	0.6
Net (gain) from asset sales	(0.1)	(0.1)
(Income) from unconsolidated affiliate	(1.9)	(1.9)
Distribution from unconsolidated affiliate	2.4	1.8
Changes in operating assets and liabilities	(6.5)	5.5
Net Cash Provided By Operating Activities	71.7	67.0
INVESTING ACTIVITIES
Property, plant and equipment	(40.9)	(48.7)
Cash used in disposition of assets	(0.1)	(0.2)
Proceeds from disposition of assets	0	0.1
Net Cash Used In Investing Activities	(41.0)	(48.8)
FINANCING ACTIVITIES
Change in notes receivable from Questar	30.3	(6.8)
Change in notes payable to Questar	49.3	(0.2)
Long-term debt repaid	(100.0)	0
Dividends paid	(15.4)	(14.5)
Net Cash Used In Financing Activities	(35.8)	(21.5)
Change in cash and cash equivalents	(5.1)	(3.3)
Beginning cash and cash equivalents	5.3	3.8
Ending cash and cash equivalents	0.2	0.5
Questar Gas [Member]
OPERATING ACTIVITIES
Net income	33.8	30.9
Adjustments to reconcile net income to net cash provided by operating activities from continuing operations:
Depreciation and amortization	24.0	24.4
Deferred income taxes	20.4	9.4
Share-based compensation	0.6	0.8
Changes in operating assets and liabilities	94.4	22.0
Net Cash Provided By Operating Activities	173.2	87.5
INVESTING ACTIVITIES
Property, plant and equipment	(55.2)	(50.9)
Cash used in disposition of assets	(1.0)	(0.8)
Proceeds from disposition of assets	0.2	0.4
Net Cash Used In Investing Activities	(56.0)	(51.3)
FINANCING ACTIVITIES
Change in notes payable to Questar	(109.6)	(33.1)
Checks outstanding in excess of cash balances	2.9	4.1
Dividends paid	(15.2)	(14.4)
Net Cash Used In Financing Activities	(121.9)	(43.4)
Change in cash and cash equivalents	(4.7)	(7.2)
Beginning cash and cash equivalents	4.7	7.2
Ending cash and cash equivalents	$ 0	$ 0