CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
OPERATING ACTIVITIES
Net income	$ 161.2	$ 212.0	$ 207.9
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	201.8	189.2	169.4
Deferred income taxes	42.4	118.6	96.2
Asset impairment	80.6	0	0
Share-based compensation	10.2	9.9	10.1
Net (gain) loss from asset sales	0.2	(5.1)	(0.2)
(Income) from unconsolidated affiliate	(3.7)	(3.7)	(3.8)
Distributions from unconsolidated affiliate	4.6	4.5	4.4
Other operating	0.9	0.4	0.1
Changes in operating assets and liabilities
Accounts receivable including unbilled gas sales	(41.5)	23.7	7.7
Inventories	(0.2)	2.5	(3.3)
Prepaid expenses and other	3.6	(2.8)	(2.1)
Interest rate hedges - current	0	7.6	(37.3)
Accounts payable and accrued expenses	33.7	(5.1)	11.7
Federal income taxes	6.2	(10.7)	37.1
Current regulatory assets and liabilities	19.2	(24.6)	31.2
Noncurrent regulatory and other assets and liabilities	(17.1)	(48.7)	(40.1)
NET CASH PROVIDED BY OPERATING ACTIVITIES	502.1	467.7	489.0
INVESTING ACTIVITIES
Property, plant and equipment	(399.4)	(370.7)	(367.7)
Wexpro acquisition of producing properties	(104.3)	0	0
Cash used in disposition of assets	(4.9)	(3.0)	(3.5)
Proceeds from disposition of assets	0.6	8.4	0.3
NET CASH USED IN INVESTING ACTIVITIES	(508.0)	(365.3)	(370.9)
FINANCING ACTIVITIES
Common stock issued	2.3	7.2	7.6
Common stock repurchased	(4.2)	(87.5)	(4.9)
Long-term debt issued, net of issuance costs	147.3	148.8	174.9
Long-term debt repaid	(42.0)	(91.5)	(182.0)
Capital lease obligation repaid	(0.7)	(0.8)	0
Change in short-term debt	13.0	44.0	(23.0)
Dividends paid	(124.6)	(117.4)	(110.1)
Tax benefits from share-based compensation	14.0	0	9.2
NET CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES	5.1	(97.2)	(128.3)
Change in cash and cash equivalents	(0.8)	5.2	(10.2)
Beginning cash and cash equivalents	16.8	11.6	21.8
Ending cash and cash equivalents	16.0	16.8	11.6
Supplemental Disclosure of Cash Paid (Received) During the Year for:
Interest	55.8	58.5	54.2
Income taxes	33.6	9.1	(29.2)
Supplemental Disclosure of Noncash Investing and Financing Transaction:
Capital lease obligation incurred		40.8
Questar Gas [Member]
OPERATING ACTIVITIES
Net income	52.8	47.1	46.1
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	54.7	52.1	49.2
Deferred income taxes	37.7	45.9	25.2
Share-based compensation	1.4	1.2	1.1
Changes in operating assets and liabilities
Accounts receivable including unbilled gas sales	(43.7)	(12.7)	5.0
Inventories	0.5	0.7	(1.3)
Prepaid expenses and other	0.2	(0.1)	(0.2)
Accounts payable and accrued expenses	29.5	7.8	(1.8)
Federal income taxes	(2.8)	1.5	6.2
Current regulatory assets and liabilities	17.6	(24.4)	37.6
Noncurrent regulatory and other assets and liabilities	5.4	(6.4)	(20.2)
NET CASH PROVIDED BY OPERATING ACTIVITIES	153.3	112.7	146.9
INVESTING ACTIVITIES
Property, plant and equipment	(166.2)	(162.1)	(121.5)
Cash used in disposition of assets	(3.9)	(2.3)	(2.2)
Proceeds from disposition of assets	0.3	0.4	0.2
Affiliated-company property, plant and equipment transfers	10.8	0	0.1
NET CASH USED IN INVESTING ACTIVITIES	(159.0)	(164.0)	(123.4)
FINANCING ACTIVITIES
Equity contribution from Questar	0	0	20.0
Long-term debt issued, net of issuance costs	149.0	148.8	0
Long-term debt repaid	(42.0)	(91.5)	(2.0)
Change in notes payable to Questar	(58.4)	23.4	(10.9)
Dividends paid	(35.5)	(33.0)	(30.3)
NET CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES	13.1	47.7	(23.2)
Change in cash and cash equivalents	7.4	(3.6)	0.3
Beginning cash and cash equivalents	1.4	5.0	4.7
Ending cash and cash equivalents	8.8	1.4	5.0
Supplemental Disclosure of Cash Paid (Received) During the Year for:
Interest	21.0	24.7	25.1
Income taxes	(13.8)	(20.4)	(3.3)
Supplemental Disclosure of Noncash Investing and Financing Transaction:
Noncash reduction in notes payable to Questar due to equity contribution	90.0
Questar Pipeline [Member]
OPERATING ACTIVITIES
Net income	8.2	64.7	67.9
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	58.1	56.8	53.9
Deferred income taxes	(14.3)	41.1	34.5
Asset impairment	80.6	0	0
Share-based compensation	2.0	2.0	1.8
Net (gain) loss from asset sales	0	(2.7)	(0.3)
(Income) from unconsolidated affiliate	(3.7)	(3.7)	(3.8)
Distributions from unconsolidated affiliate	4.6	4.5	4.4
Other operating	0.5	0.4	0.1
Changes in operating assets and liabilities
Accounts receivable including unbilled gas sales	(8.5)	(2.1)	(0.8)
Inventories	(0.9)	0.2	(0.2)
Prepaid expenses and other	3.3	(3.3)	0
Interest rate hedges - current	0	0	(37.3)
Accounts payable and accrued expenses	0.4	(3.4)	0.8
Federal income taxes	2.9	0	1.1
Current regulatory assets and liabilities	2.1	(0.9)	(5.0)
NET CASH PROVIDED BY OPERATING ACTIVITIES	135.3	153.6	117.1
INVESTING ACTIVITIES
Property, plant and equipment	(73.4)	(60.6)	(104.5)
Cash used in disposition of assets	(1.0)	(0.7)	(1.3)
Proceeds from disposition of assets	0.1	4.3	0.1
Affiliated-company property, plant and equipment transfers	(10.7)	0	(0.1)
NET CASH USED IN INVESTING ACTIVITIES	(85.0)	(57.0)	(105.8)
FINANCING ACTIVITIES
Long-term debt issued, net of issuance costs	0	0	176.2
Long-term debt repaid	0	0	(180.0)
Change in notes receivable from Questar	9.3	(29.9)	21.5
Dividends paid	(64.0)	(63.0)	(30.9)
NET CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES	(54.7)	(92.9)	(13.2)
Change in cash and cash equivalents	(4.4)	3.7	(1.9)
Beginning cash and cash equivalents	7.1	3.4	5.3
Ending cash and cash equivalents	2.7	7.1	3.4
Supplemental Disclosure of Cash Paid (Received) During the Year for:
Interest	25.2	25.2	24.7
Income taxes	$ 11.0	$ (3.8)	$ 2.9