CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Current Assets
Cash and cash equivalents	$ 0.0	$ 25.0	$ 0.0
Accounts receivable, net	56.6	168.0	53.3
Unbilled gas accounts receivable	11.0	91.3	11.6
Gas stored underground	26.2	45.1	30.6
Materials and supplies	27.8	28.4	30.7
Current regulatory assets	21.0	70.0	57.1
Prepaid expenses and other	20.0	12.3	10.2
Total Current Assets	162.6	440.1	193.5
Property, Plant and Equipment	6,313.4	6,182.0	6,057.2
Accumulated depreciation, depletion and amortization	(2,424.2)	(2,333.3)	(2,272.5)
Net Property, Plant and Equipment	3,889.2	3,848.7	3,784.7
Investment in unconsolidated affiliate	23.5	23.9	24.3
Noncurrent regulatory assets	19.7	14.9	23.7
Other noncurrent assets	45.6	44.2	43.9
TOTAL ASSETS	4,140.6	4,371.8	4,070.1
Current Liabilities
Checks outstanding in excess of cash balances	4.0	0.0	2.5
Short-term debt	459.0	457.6	228.0
Accounts payable and accrued expenses	159.7	224.8	201.0
Current regulatory liabilities	34.2	6.4	2.6
Current portion of long-term debt and capital lease obligation	1.3	251.3	277.0
Total Current Liabilities	658.2	940.1	711.1
Long-term debt and capital lease obligation, less current portion	997.9	998.2	998.6
Deferred income taxes	783.7	779.5	707.3
Asset retirement obligations	71.4	67.6	70.6
Defined benefit pension plan and other postretirement benefits	108.7	123.0	125.1
Noncurrent regulatory liabilities	85.1	75.6	74.9
Customer contributions in aid of construction	23.1	23.7	27.4
Other noncurrent liabilities	52.2	49.0	46.3
COMMON SHAREHOLDERS' EQUITY
Common stock	475.6	469.0	480.8
Retained earnings	1,065.5	1,031.4	1,021.8
Accumulated other comprehensive (loss)	(180.8)	(185.3)	(193.8)
Total Common Shareholders' Equity	1,360.3	1,315.1	1,308.8
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	4,140.6	4,371.8	4,070.1
Questar Gas [Member]
Current Assets
Cash and cash equivalents	0.0	10.5	0.0
Accounts receivable, net	36.6	112.0	29.6
Unbilled gas accounts receivable	11.0	91.0	11.6
Accounts receivable from affiliates	72.1	69.2	68.3
Gas stored underground	23.1	43.9	26.1
Materials and supplies	16.7	17.1	18.7
Current regulatory assets	20.6	69.8	56.3
Prepaid expenses and other	4.2	3.5	3.8
Total Current Assets	184.3	417.0	214.4
Property, Plant and Equipment	2,684.8	2,570.3	2,455.4
Accumulated depreciation, depletion and amortization	(827.6)	(812.2)	(799.9)
Net Property, Plant and Equipment	1,857.2	1,758.1	1,655.5
Noncurrent regulatory assets	16.5	11.9	19.8
Other noncurrent assets	5.7	5.7	5.7
TOTAL ASSETS	2,063.7	2,192.7	1,895.4
Current Liabilities
Checks outstanding in excess of cash balances	5.1	0.0	4.1
Notes payable to Questar	129.0	273.3	59.7
Accounts payable and accrued expenses	81.2	122.5	106.7
Accounts payable to affiliates	69.7	74.5	77.8
Customer advances	13.7	34.3	18.0
Current regulatory liabilities	32.8	4.0	1.0
Total Current Liabilities	331.5	508.6	267.3
Long-term debt, less current portion	531.4	531.2	531.0
Deferred income taxes	449.2	436.7	382.0
Noncurrent regulatory liabilities	74.7	65.6	65.5
Customer contributions in aid of construction	23.1	23.7	27.4
Other noncurrent liabilities	2.3	2.2	2.5
COMMON SHAREHOLDERS' EQUITY
Common stock	23.0	23.0	23.0
Additional paid-in capital	267.6	266.8	266.1
Retained earnings	360.9	334.9	330.6
Total Common Shareholders' Equity	651.5	624.7	619.7
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	2,063.7	2,192.7	1,895.4
Questar Pipeline [Member]
Current Assets
Cash and cash equivalents	1.6	10.2	1.0
Notes receivable from Questar	34.6	6.0	34.0
Accounts receivable, net	16.6	29.6	17.0
Accounts receivable from affiliates	51.9	49.8	47.1
Gas stored underground	3.1	1.2	4.5
Materials and supplies	6.5	6.7	7.4
Current regulatory assets	0.4	0.2	0.8
Prepaid expenses and other	3.0	4.4	2.8
Total Current Assets	117.7	108.1	114.6
Property, Plant and Equipment	1,860.4	1,851.1	1,843.6
Accumulated depreciation, depletion and amortization	(732.8)	(709.7)	(697.8)
Net Property, Plant and Equipment	1,127.6	1,141.4	1,145.8
Investment in unconsolidated affiliate	23.5	23.9	24.3
Noncurrent regulatory and other assets	7.4	7.1	8.0
TOTAL ASSETS	1,276.2	1,280.5	1,292.7
Current Liabilities
Accounts payable and accrued expenses	16.8	16.1	21.8
Accounts payable to affiliates	12.3	15.8	9.1
Current regulatory liabilities	1.4	2.4	1.6
Current portion of long-term debt	0.0	0.0	25.1
Total Current Liabilities	30.5	34.3	57.6
Long-term debt, less current portion	431.2	431.0	430.9
Deferred income taxes	251.6	249.9	238.6
Noncurrent regulatory and other liabilities	17.7	16.3	16.0
COMMON SHAREHOLDERS' EQUITY
Common stock	6.6	6.6	6.6
Additional paid-in capital	354.3	353.4	352.7
Retained earnings	207.1	211.3	212.8
Accumulated other comprehensive (loss)	(22.8)	(22.3)	(22.5)
Total Common Shareholders' Equity	545.2	549.0	549.6
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	$ 1,276.2	$ 1,280.5	$ 1,292.7