CONSOLIDATED BALANCE SHEETS (USD $)	Dec. 31, 2012	Dec. 31, 2011
Current Assets
Cash and cash equivalents	$ 16,800,000	$ 11,600,000
Federal income taxes receivable	10,700,000	0
Accounts receivable, net	103,600,000	123,900,000
Unbilled gas accounts receivable	78,300,000	75,400,000
Inventories at lower of average cost or market:
Gas stored underground	39,000,000	40,300,000
Materials and supplies	24,500,000	25,700,000
Current regulatory assets	46,700,000	31,700,000
Prepaid expenses and other	13,100,000	10,700,000
Deferred income taxes - current	13,000,000	16,100,000
Total Current Assets	345,700,000	335,400,000
Property, Plant and Equipment
Distribution property, plant and equipment	2,040,900,000	1,927,000,000
Transportation property, plant and equipment	1,840,100,000	1,790,400,000
Cost-of-service gas and oil property, plant and equipment, successful efforts method	1,397,600,000	1,253,600,000
Other	54,700,000	13,100,000
Total property, plant and equipment	5,333,300,000	4,984,100,000
Distribution accumulated depreciation and amortization	(762,800,000)	(749,600,000)
Transportation accumulated depreciation and amortization	(629,300,000)	(586,700,000)
Cost-of-service gas and oil accumulated depreciation depletion and amortization	(617,200,000)	(545,000,000)
Other accumulated depreciation and amortization	(7,000,000)	(4,400,000)
Total accumulated depreciation, depletion and amortization	(2,016,300,000)	(1,885,700,000)
Total Property, Plant and Equipment, net	3,317,000,000	3,098,400,000
Investment in unconsolidated affiliate	26,500,000	27,300,000
Other Assets
Goodwill	9,800,000	9,800,000
Regulatory assets	21,600,000	21,000,000
Other noncurrent assets	36,500,000	40,900,000
Total Other Assets	67,900,000	71,700,000
TOTAL ASSETS	3,757,100,000	3,532,800,000
Current Liabilities
Short-term debt	263,000,000	219,000,000
Accounts payable and accrued expenses	167,500,000	175,700,000
Production and other taxes	28,000,000	31,500,000
Customer advances	30,200,000	25,000,000
Interest payable	9,500,000	10,700,000
Current regulatory liabilities	5,800,000	15,400,000
Current portion of long-term debt	42,000,000	91,500,000
Current portion of capital lease obligation	700,000	0
Total Current Liabilities	546,700,000	568,800,000
Long-term debt, less current portion	1,098,900,000	993,000,000
Capital lease obligation	39,300,000	0
Deferred income taxes	603,400,000	500,200,000
Asset retirement obligations	67,200,000	63,800,000
Defined benefit pension plan	246,900,000	255,000,000
Other postretirement benefits	56,800,000	54,700,000
Customer contributions in aid of construction	22,900,000	26,600,000
Regulatory and other noncurrent liabilities	39,400,000	37,200,000
Commitments and contingencies - Note 8
COMMON SHAREHOLDERS' EQUITY
Common stock	442,400,000	514,700,000
Retained earnings	839,500,000	744,900,000
Accumulated other comprehensive loss	(246,300,000)	(226,100,000)
Total Common Shareholders' Equity	1,035,600,000	1,033,500,000
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	3,757,100,000	3,532,800,000
Questar Gas [Member]
Current Assets
Cash and cash equivalents	1,400,000	5,000,000
Federal income taxes receivable	0	1,500,000
Accounts receivable, net	67,000,000	76,100,000
Unbilled gas accounts receivable	78,200,000	75,200,000
Accounts receivable from affiliates	31,800,000	1,800,000
Inventories at lower of average cost or market:
Gas stored underground	38,300,000	40,300,000
Materials and supplies	13,500,000	12,200,000
Current regulatory assets	41,000,000	26,500,000
Prepaid expenses and other	3,200,000	3,100,000
Deferred income taxes - current	1,500,000	5,600,000
Total Current Assets	275,900,000	247,300,000
Property, Plant and Equipment
Distribution property, plant and equipment	1,690,500,000	1,583,100,000
Other	281,600,000	284,400,000
Construction work in progress	68,800,000	59,500,000
Total property, plant and equipment	2,040,900,000	1,927,000,000
Total accumulated depreciation, depletion and amortization	(762,800,000)	(749,600,000)
Total Property, Plant and Equipment, net	1,278,100,000	1,177,400,000
Other Assets
Goodwill	5,600,000	5,600,000
Regulatory assets	16,400,000	15,100,000
Other noncurrent assets	3,100,000	2,300,000
Total Other Assets	25,100,000	23,000,000
TOTAL ASSETS	1,579,100,000	1,447,700,000
Current Liabilities
Notes payable to Questar	166,100,000	142,700,000
Accounts payable and accrued expenses	100,500,000	106,500,000
Accounts payable to affiliates	50,900,000	41,900,000
Customer advances	30,200,000	25,000,000
Interest payable	4,500,000	5,800,000
Current regulatory liabilities	4,300,000	14,200,000
Current portion of long-term debt	42,000,000	91,500,000
Total Current Liabilities	398,500,000	427,600,000
Long-term debt, less current portion	384,500,000	276,500,000
Deferred income taxes	301,600,000	259,800,000
Asset retirement obligations	500,000	700,000
Customer contributions in aid of construction	22,900,000	26,600,000
Regulatory and other noncurrent liabilities	4,000,000	4,800,000
Commitments and contingencies - Note 8
COMMON SHAREHOLDERS' EQUITY
Common stock	23,000,000	23,000,000
Additional paid-in capital	172,500,000	171,400,000
Retained earnings	272,100,000	258,000,000
Total Common Shareholders' Equity	467,600,000	452,400,000
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	1,579,100,000	1,447,700,000
Questar Pipeline [Member]
Current Assets
Cash and cash equivalents	7,100,000	3,400,000
Notes receivable from Questar	38,700,000	8,800,000
Accounts receivable, net	19,100,000	19,100,000
Accounts receivable from affiliates	27,500,000	20,200,000
Inventories at lower of average cost or market:
Materials and supplies	7,200,000	7,400,000
Current regulatory assets	5,700,000	5,200,000
Prepaid expenses and other	7,700,000	4,400,000
Deferred income taxes - current	1,600,000	1,800,000
Total Current Assets	114,600,000	70,300,000
Property, Plant and Equipment
Transportation property, plant and equipment	1,394,700,000	1,358,500,000
Storage	288,900,000	287,800,000
Processing	25,700,000	25,400,000
General and intangible	81,500,000	65,300,000
Construction work in progress	49,300,000	53,400,000
Total property, plant and equipment	1,840,100,000	1,790,400,000
Total accumulated depreciation, depletion and amortization	(629,300,000)	(586,700,000)
Total Property, Plant and Equipment, net	1,210,800,000	1,203,700,000
Investment in unconsolidated affiliate	26,500,000	27,300,000
Other Assets
Goodwill	4,200,000	4,200,000
Regulatory assets	5,200,000	5,900,000
Regulatory and other noncurrent assets	9,000,000	10,100,000
Total Other Assets	13,200,000	14,300,000
TOTAL ASSETS	1,365,100,000	1,315,600,000
Current Liabilities
Accounts payable and accrued expenses	23,600,000	29,700,000
Accounts payable to affiliates	16,900,000	5,500,000
Interest payable	2,100,000	2,000,000
Current regulatory liabilities	1,500,000	1,200,000
Total Current Liabilities	44,100,000	38,400,000
Long-term debt, less current portion	458,900,000	459,000,000
Deferred income taxes	242,500,000	201,400,000
Asset retirement obligations	2,100,000	2,800,000
Regulatory and other noncurrent liabilities	13,800,000	14,700,000
Commitments and contingencies - Note 8
COMMON SHAREHOLDERS' EQUITY
Common stock	6,600,000	6,600,000
Additional paid-in capital	347,500,000	345,700,000
Retained earnings	274,900,000	273,200,000
Accumulated other comprehensive loss	(23,200,000)	(23,400,000)
Total Common Shareholders' Equity	605,800,000	602,100,000
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	$ 1,365,100,000	$ 1,315,600,000