CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Current Assets
Cash and cash equivalents	$ 0.4	$ 25.0	$ 4.8
Accounts receivable, net	107.1	168.0	104.5
Unbilled gas accounts receivable	58.7	91.3	41.5
Gas stored underground	9.6	45.1	12.4
Materials and supplies	30.1	28.4	28.7
Current regulatory assets	20.3	70.0	43.0
Prepaid expenses and other	8.4	12.3	8.7
Total Current Assets	234.6	440.1	243.6
Property, Plant and Equipment	6,240.9	6,182.0	6,033.1
Accumulated depreciation, depletion and amortization	(2,380.4)	(2,333.3)	(2,277.2)
Net Property, Plant and Equipment	3,860.5	3,848.7	3,755.9
Investment in unconsolidated affiliate	23.7	23.9	24.5
Noncurrent regulatory assets	14.4	9.3	17.3
Other noncurrent assets	46.0	44.2	43.4
TOTAL ASSETS	4,179.2	4,366.2	4,084.7
Current Liabilities
Short-term debt	458.5	457.6	214.0
Accounts payable and accrued expenses	177.2	224.8	200.5
Current regulatory liabilities	63.6	6.4	5.2
Current portion of long-term debt and capital lease obligation	1.2	251.3	277.4
Total Current Liabilities	700.5	940.1	697.1
Long-term debt and capital lease obligation, less current portion	992.7	992.6	992.5
Deferred income taxes	776.0	779.5	708.4
Asset retirement obligations	70.5	67.6	75.0
Defined benefit pension plan and other postretirement benefits	117.3	123.0	155.7
Noncurrent regulatory liabilities	82.1	75.6	72.5
Customer contributions in aid of construction	23.4	23.7	28.0
Other noncurrent liabilities	56.0	49.0	57.2
COMMON SHAREHOLDERS' EQUITY
Common stock	472.4	469.0	477.6
Retained earnings	1,071.2	1,031.4	1,018.2
Accumulated other comprehensive (loss)	(182.9)	(185.3)	(197.5)
Total Common Shareholders' Equity	1,360.7	1,315.1	1,298.3
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	4,179.2	4,366.2	4,084.7
Questar Gas [Member]
Current Assets
Cash and cash equivalents	0.0	10.5	0.0
Accounts receivable, net	97.3	112.0	81.2
Unbilled gas accounts receivable	58.7	91.0	41.5
Accounts receivable from affiliates	71.5	69.2	56.3
Gas stored underground	7.1	43.9	9.5
Materials and supplies	18.8	17.1	17.3
Current regulatory assets	20.2	69.8	42.1
Prepaid expenses and other	2.9	3.5	2.4
Total Current Assets	276.5	417.0	250.3
Property, Plant and Equipment	2,618.8	2,570.3	2,400.7
Accumulated depreciation, depletion and amortization	(820.3)	(812.2)	(791.5)
Net Property, Plant and Equipment	1,798.5	1,758.1	1,609.2
Noncurrent regulatory assets	13.5	8.1	16.1
Other noncurrent assets	5.6	5.7	5.7
TOTAL ASSETS	2,094.1	2,188.9	1,881.3
Current Liabilities
Checks outstanding in excess of cash balances	0.7	0.0	0.4
Notes payable to Questar	140.5	273.3	35.8
Accounts payable and accrued expenses	79.7	122.5	126.0
Accounts payable to affiliates	75.3	74.5	71.4
Customer advances	9.8	34.3	9.5
Current regulatory liabilities	61.8	4.0	4.3
Total Current Liabilities	367.8	508.6	247.4
Long-term debt, less current portion	527.6	527.4	526.8
Deferred income taxes	438.4	436.7	381.4
Noncurrent regulatory liabilities	71.9	65.6	63.3
Customer contributions in aid of construction	23.4	23.7	28.0
Other noncurrent liabilities	2.3	2.2	2.8
COMMON SHAREHOLDERS' EQUITY
Common stock	23.0	23.0	23.0
Additional paid-in capital	267.2	266.8	265.7
Retained earnings	372.5	334.9	342.9
Total Common Shareholders' Equity	662.7	624.7	631.6
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	2,094.1	2,188.9	1,881.3
Questar Pipeline [Member]
Current Assets
Cash and cash equivalents	1.2	10.2	6.1
Notes receivable from Questar	33.2	6.0	35.9
Accounts receivable, net	17.2	29.6	16.8
Accounts receivable from affiliates	50.4	49.8	44.3
Gas stored underground	2.5	1.2	2.9
Materials and supplies	6.3	6.7	7.1
Current regulatory assets	0.1	0.2	0.9
Prepaid expenses and other	2.7	4.4	3.6
Total Current Assets	113.6	108.1	117.6
Property, Plant and Equipment	1,857.1	1,851.1	1,837.5
Accumulated depreciation, depletion and amortization	(722.8)	(709.7)	(687.9)
Net Property, Plant and Equipment	1,134.3	1,141.4	1,149.6
Investment in unconsolidated affiliate	23.7	23.9	24.5
Noncurrent regulatory and other assets	5.1	5.3	5.5
TOTAL ASSETS	1,276.7	1,278.7	1,297.2
Current Liabilities
Accounts payable and accrued expenses	20.7	16.1	33.9
Accounts payable to affiliates	8.6	15.8	3.4
Current regulatory liabilities	1.8	2.4	0.9
Current portion of long-term debt	0.0	0.0	25.1
Total Current Liabilities	31.1	34.3	63.3
Long-term debt, less current portion	429.4	429.2	428.8
Deferred income taxes	251.2	249.9	239.4
Noncurrent regulatory and other liabilities	17.4	16.3	16.0
COMMON SHAREHOLDERS' EQUITY
Common stock	6.6	6.6	6.6
Additional paid-in capital	353.9	353.4	351.9
Retained earnings	209.5	211.3	213.6
Accumulated other comprehensive (loss)	(22.4)	(22.3)	(22.4)
Total Common Shareholders' Equity	547.6	549.0	549.7
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	$ 1,276.7	$ 1,278.7	$ 1,297.2