Operations by Line of Business (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Revenues
Total Revenues	$ 536.7	$ 910.0	$ 1,636.9	$ 2,614.7
Operating expenses
Purchased gas and oil expense	175.1	288.4	561.7	775.5
Lease operating expense	56.7	61.1	175.6	177.0
Natural gas, oil and NGL transportation and other handling costs	78.1	71.1	216.2	198.5
Gathering, processing and other	1.3	1.4	4.4	4.8
General and administrative	42.0	49.4	140.7	147.0
Production and property taxes	30.2	59.4	90.7	160.8
Depreciation, depletion and amortization	238.1	251.4	649.3	712.5
Other operating expenses	15.8	0.9	38.2	8.3
Total operating expenses	637.3	783.1	1,876.8	2,184.4
Net gain (loss) from asset sales	12.9	(11.8)	6.9	(210.3)
Operating income (loss)	(87.7)	115.1	(233.0)	220.0
Realized and unrealized gains (losses) on derivative contracts	153.6	155.7	168.5	(13.2)
Interest and other income (expense)	0.3	4.2	1.5	7.8
Income from unconsolidated affiliates	0.0	0.1	0.0	0.2
Interest expense	(36.4)	(41.5)	(109.4)	(128.4)
Income (loss) before income taxes	29.8	233.6	(172.4)	86.4
Income taxes	(8.7)	(79.9)	61.6	(26.1)
Income from continuing operations	21.1	153.7	(110.8)	60.3
Net income from discontinued operations, net of income tax	0.0	17.4	0.0	58.2
Net income (loss)	21.1	171.1	(110.8)	118.5
Unaffiliated customers [Member]
Revenues
Total Revenues	536.7	910.0	1,636.9	2,614.7
Affiliated customers [Member]
Revenues
Total Revenues	0.0	0.0	0.0	0.0
QEP Energy [Member]
Revenues
Total Revenues	382.6	652.9	1,143.8	1,953.3
Operating expenses
Purchased gas and oil expense	23.6	32.8	71.6	120.9
Lease operating expense	56.7	61.1	175.6	177.0
Natural gas, oil and NGL transportation and other handling costs	80.1	75.2	223.0	211.8
Gathering, processing and other	0.0	0.0	0.0	0.0
General and administrative	41.2	49.0	137.4	146.5
Production and property taxes	29.9	59.3	88.6	159.8
Depreciation, depletion and amortization	235.7	249.0	641.6	704.7
Other operating expenses	15.8	0.9	38.2	8.3
Total operating expenses	483.0	527.3	1,376.0	1,529.0
Net gain (loss) from asset sales	13.2	(11.9)	11.9	(210.3)
Operating income (loss)	(87.2)	113.7	(220.3)	214.0
Realized and unrealized gains (losses) on derivative contracts	152.3	154.1	166.9	(9.7)
Interest and other income (expense)	0.9	3.9	0.5	7.4
Income from unconsolidated affiliates		0.1		0.2
Interest expense	(52.4)	(57.0)	(152.2)	(162.5)
Income (loss) before income taxes	13.6	214.8	(205.1)	49.4
Income taxes	(2.8)	(69.1)	73.2	(9.0)
Income from continuing operations		145.7		40.4
Net income from discontinued operations, net of income tax		0.0		0.0
Net income (loss)	10.8	145.7	(131.9)	40.4
QEP Energy [Member] | Unaffiliated customers [Member]
Revenues
Total Revenues	382.6	652.9	1,143.8	1,953.3
QEP Energy [Member] | Affiliated customers [Member]
Revenues
Total Revenues	0.0	0.0	0.0	0.0
QEP Marketing and Other [Member]
Revenues
Total Revenues	417.5	674.9	1,212.1	1,794.3
Operating expenses
Purchased gas and oil expense	412.1	668.3	1,200.3	1,771.6
Lease operating expense	0.0	0.0	0.0	0.0
Natural gas, oil and NGL transportation and other handling costs	0.0	0.0	0.0	0.0
Gathering, processing and other	1.3	1.4	4.4	4.8
General and administrative	1.6	1.4	5.3	3.1
Production and property taxes	0.3	0.1	2.1	1.0
Depreciation, depletion and amortization	2.4	2.4	7.7	7.8
Other operating expenses	0.0	0.0	0.0	0.0
Total operating expenses	417.7	673.6	1,219.8	1,788.3
Net gain (loss) from asset sales	(0.3)	0.1	(5.0)	0.0
Operating income (loss)	(0.5)	1.4	(12.7)	6.0
Realized and unrealized gains (losses) on derivative contracts	1.3	1.6	1.6	(3.5)
Interest and other income (expense)	52.0	56.6	153.1	162.0
Income from unconsolidated affiliates		0.0		0.0
Interest expense	(36.6)	(40.8)	(109.3)	(127.5)
Income (loss) before income taxes	16.2	18.8	32.7	37.0
Income taxes	(5.9)	(10.8)	(11.6)	(17.1)
Income from continuing operations		8.0		19.9
Net income from discontinued operations, net of income tax		0.0		0.0
Net income (loss)	10.3	8.0	21.1	19.9
QEP Marketing and Other [Member] | Unaffiliated customers [Member]
Revenues
Total Revenues	154.1	257.1	493.1	661.4
QEP Marketing and Other [Member] | Affiliated customers [Member]
Revenues
Total Revenues	263.4	417.8	719.0	1,132.9
Elimination [Member]
Revenues
Total Revenues	(263.4)	(417.8)	(719.0)	(1,132.9)
Operating expenses
Purchased gas and oil expense	(260.6)	(412.7)	(710.2)	(1,117.0)
Lease operating expense	0.0	0.0	0.0	0.0
Natural gas, oil and NGL transportation and other handling costs	(2.0)	(4.1)	(6.8)	(13.3)
Gathering, processing and other	0.0	0.0	0.0	0.0
General and administrative	(0.8)	(1.0)	(2.0)	(2.6)
Production and property taxes	0.0	0.0	0.0	0.0
Depreciation, depletion and amortization	0.0	0.0	0.0	0.0
Other operating expenses	0.0	0.0	0.0	0.0
Total operating expenses	(263.4)	(417.8)	(719.0)	(1,132.9)
Net gain (loss) from asset sales	0.0	0.0	0.0	0.0
Operating income (loss)	0.0	0.0	0.0	0.0
Realized and unrealized gains (losses) on derivative contracts	0.0	0.0	0.0	0.0
Interest and other income (expense)	(52.6)	(56.3)	(152.1)	(161.6)
Income from unconsolidated affiliates		0.0		0.0
Interest expense	52.6	56.3	152.1	161.6
Income (loss) before income taxes	0.0	0.0	0.0	0.0
Income taxes	0.0	0.0	0.0	0.0
Income from continuing operations		0.0		0.0
Net income from discontinued operations, net of income tax		0.0		0.0
Net income (loss)	0.0	0.0	0.0	0.0
Elimination [Member] | Unaffiliated customers [Member]
Revenues
Total Revenues	0.0	0.0	0.0	0.0
Elimination [Member] | Affiliated customers [Member]
Revenues
Total Revenues	$ (263.4)	(417.8)	$ (719.0)	(1,132.9)
Discontinued Operations [Member]
Revenues
Total Revenues		0.0		0.0
Operating expenses
Purchased gas and oil expense		0.0		0.0
Lease operating expense		0.0		0.0
Natural gas, oil and NGL transportation and other handling costs		0.0		0.0
Gathering, processing and other		0.0		0.0
General and administrative		0.0		0.0
Production and property taxes		0.0		0.0
Depreciation, depletion and amortization		0.0		0.0
Other operating expenses		0.0		0.0
Total operating expenses		0.0		0.0
Net gain (loss) from asset sales		0.0		0.0
Operating income (loss)		0.0		0.0
Realized and unrealized gains (losses) on derivative contracts		0.0		0.0
Interest and other income (expense)		0.0		0.0
Income from unconsolidated affiliates		0.0		0.0
Interest expense		0.0		0.0
Income (loss) before income taxes		0.0		0.0
Income taxes		0.0		0.0
Income from continuing operations		0.0		0.0
Net income from discontinued operations, net of income tax		17.4		58.2
Net income (loss)		17.4		58.2
Discontinued Operations [Member] | Unaffiliated customers [Member]
Revenues
Total Revenues		0.0		0.0
Discontinued Operations [Member] | Affiliated customers [Member]
Revenues
Total Revenues		$ 0.0		$ 0.0