CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Current Assets
Cash and cash equivalents	$ 0.0	$ 32.0	$ 7.3
Accounts receivable, net	62.3	118.1	57.3
Unbilled gas accounts receivable	11.2	93.7	12.8
Gas stored underground	75.1	43.7	69.3
Materials and supplies	29.6	30.4	25.2
Current regulatory assets	89.9	79.6	84.2
Prepaid expenses and other	8.2	11.2	6.3
Deferred income taxes - current	0.0	5.8	14.7
Total Current Assets	276.3	414.5	277.1
Property, Plant and Equipment	6,129.9	5,961.5	5,852.3
Accumulated depreciation, depletion and amortization	(2,313.9)	(2,226.0)	(2,185.2)
Net Property, Plant and Equipment	3,816.0	3,735.5	3,667.1
Investment in unconsolidated affiliate	24.5	24.7	24.9
Noncurrent regulatory assets	22.7	25.0	18.6
Other noncurrent assets	47.9	50.0	50.2
TOTAL ASSETS	4,187.4	4,249.7	4,037.9
Current Liabilities
Checks outstanding in excess of cash balances	2.8	0.0	0.0
Short-term debt	305.0	347.0	234.0
Accounts payable and accrued expenses	225.9	234.9	225.4
Current regulatory liabilities	3.3	13.4	11.0
Deferred income taxes - current	2.8	0.0	0.0
Current portion of long-term debt and capital lease obligation	276.8	26.1	1.0
Total Current Liabilities	816.6	621.4	471.4
Long-term debt and capital lease obligation, less current portion	1,004.4	1,257.5	1,283.3
Deferred income taxes	730.9	715.6	718.5
Asset retirement obligations	71.0	69.3	69.2
Defined benefit pension plan and other postretirement benefits	119.3	185.7	73.3
Noncurrent regulatory liabilities	77.4	69.9	67.9
Customer contributions in aid of construction	26.0	29.2	29.6
Other noncurrent liabilities	48.5	54.9	45.4
COMMON SHAREHOLDERS' EQUITY
Common stock	465.4	476.8	471.5
Retained earnings	1,017.3	970.7	941.6
Accumulated other comprehensive (loss)	(189.4)	(201.3)	(133.8)
Total Common Shareholders' Equity	1,293.3	1,246.2	1,279.3
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	4,187.4	4,249.7	4,037.9
Questar Gas [Member]
Current Assets
Cash and cash equivalents	0.0	19.8	0.0
Accounts receivable, net	38.7	66.4	27.6
Unbilled gas accounts receivable	10.9	93.7	12.8
Accounts receivable from affiliates	67.5	45.2	44.7
Gas stored underground	68.9	40.3	66.8
Materials and supplies	18.2	19.2	14.0
Current regulatory assets	89.9	78.3	82.6
Prepaid expenses and other	2.7	3.5	2.6
Deferred income taxes - current	0.0	0.0	3.0
Total Current Assets	296.8	366.4	254.1
Property, Plant and Equipment	2,515.6	2,352.3	2,315.1
Accumulated depreciation, depletion and amortization	(806.2)	(780.3)	(770.4)
Net Property, Plant and Equipment	1,709.4	1,572.0	1,544.7
Noncurrent regulatory assets	19.3	21.3	14.4
Other noncurrent assets	9.0	9.3	9.3
TOTAL ASSETS	2,034.5	1,969.0	1,822.5
Current Liabilities
Checks outstanding in excess of cash balances	3.4	0.0	2.1
Notes payable to Questar	180.0	119.3	90.8
Accounts payable and accrued expenses	110.0	111.9	91.8
Accounts payable to affiliates	71.4	78.7	52.2
Dividends payable to Questar	0.0	9.0	0.0
Customer advances	35.3	29.4	23.2
Current regulatory liabilities	0.5	12.5	10.4
Deferred income taxes - current	14.8	6.3	0.0
Total Current Liabilities	415.4	367.1	270.5
Long-term debt, less current portion	534.5	534.5	534.5
Deferred income taxes	387.0	377.5	348.5
Noncurrent regulatory liabilities	67.7	60.9	59.1
Customer contributions in aid of construction	26.0	29.2	29.6
Other noncurrent liabilities	2.2	2.8	2.8
COMMON SHAREHOLDERS' EQUITY
Common stock	23.0	23.0	23.0
Additional paid-in capital	266.4	265.4	264.9
Retained earnings	312.3	308.6	289.6
Total Common Shareholders' Equity	601.7	597.0	577.5
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	2,034.5	1,969.0	1,822.5
Questar Pipeline [Member]
Current Assets
Cash and cash equivalents	1.1	7.4	0.4
Notes receivable from Questar	48.2	40.1	35.2
Accounts receivable, net	16.5	17.9	17.3
Accounts receivable from affiliates	47.6	39.2	37.8
Gas stored underground	6.2	3.4	2.5
Materials and supplies	6.9	6.9	6.9
Current regulatory assets	0.0	1.3	1.6
Prepaid expenses and other	1.4	4.3	1.7
Deferred income taxes - current	1.9	1.9	1.8
Total Current Assets	129.8	122.4	105.2
Property, Plant and Equipment	1,850.9	1,827.7	1,824.0
Accumulated depreciation, depletion and amortization	(706.7)	(673.9)	(662.9)
Net Property, Plant and Equipment	1,144.2	1,153.8	1,161.1
Investment in unconsolidated affiliate	24.5	24.7	24.9
Noncurrent regulatory and other assets	10.3	10.8	11.4
TOTAL ASSETS	1,308.8	1,311.7	1,302.6
Current Liabilities
Accounts payable and accrued expenses	28.0	21.7	41.1
Accounts payable to affiliates	11.5	5.8	3.6
Dividends payable to Questar	0.0	16.0	0.0
Current regulatory liabilities	2.8	0.9	0.6
Current portion of long-term debt	25.1	25.1	0.0
Total Current Liabilities	67.4	69.5	45.3
Long-term debt, less current portion	433.6	433.7	458.8
Deferred income taxes	241.9	241.4	230.0
Noncurrent regulatory and other liabilities	16.5	15.9	16.1
COMMON SHAREHOLDERS' EQUITY
Common stock	6.6	6.6	6.6
Additional paid-in capital	353.0	351.4	351.0
Retained earnings	212.0	215.7	217.4
Accumulated other comprehensive (loss)	(22.2)	(22.5)	(22.6)
Total Common Shareholders' Equity	549.4	551.2	552.4
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	$ 1,308.8	$ 1,311.7	$ 1,302.6