Operations by Line of Business (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Revenues
Total Revenues	$ 491.6	$ 817.5
Operating expenses
Purchased gas and oil expense	169.4	237.9
Lease operating expense	61.8	56.4
Natural gas, oil and NGL transportation and other handling costs	65.1	59.9
Gathering, processing and other	1.7	1.6
General and administrative	47.4	45.3
Production and property taxes	27.8	47.9
Depreciation, depletion and amortization	195.4	225.9
Other operating expenses	21.1	4.2
Total operating expenses	589.7	679.1
Net gain (loss) from asset sales	(30.5)	2.4
Operating income (loss)	(128.6)	140.8
Realized and unrealized gains (losses) on derivative contracts	80.9	(80.9)
Interest and other income (expense)	(2.6)	2.9
Interest expense	(36.8)	(41.9)
Income (loss) before income taxes	(87.1)	20.9
Income taxes	31.5	(8.2)
Income from continuing operations	(55.6)	12.7
NET INCOME (LOSS)	0	27.0
Net income (loss)	(55.6)	39.7
Assets	8,524.4	10,535.6	9,286.8
Unaffiliated customers [Member]
Revenues
Total Revenues	491.6	817.5
Affiliated customers [Member]
Revenues
Total Revenues	0	0
QEP Energy [Member]
Revenues
Total Revenues	353.3	613.2
Operating expenses
Purchased gas and oil expense	31.2	38.0
Lease operating expense	61.8	56.4
Natural gas, oil and NGL transportation and other handling costs	67.4	64.5
Gathering, processing and other	0	0
General and administrative	46.2	45.0
Production and property taxes	27.5	47.4
Depreciation, depletion and amortization	192.7	223.4
Other operating expenses	21.1	4.2
Total operating expenses	447.9	478.9
Net gain (loss) from asset sales	(27.8)	2.4
Operating income (loss)	(122.4)	136.7
Realized and unrealized gains (losses) on derivative contracts	80.2	(78.5)
Interest and other income (expense)	(3.5)	2.9
Interest expense	(47.2)	(48.9)
Income (loss) before income taxes	(92.9)	12.2
Income taxes	(33.6)	(7.1)
Income from continuing operations		5.1
NET INCOME (LOSS)		0
Net income (loss)	(59.3)	5.1
Assets		9,004.1
QEP Energy [Member] | Unaffiliated customers [Member]
Revenues
Total Revenues	353.3	613.2
QEP Energy [Member] | Affiliated customers [Member]
Revenues
Total Revenues	0	0
QEP Marketing and Other [Member]
Revenues
Total Revenues	345.8	507.8
Operating expenses
Purchased gas and oil expense	342.8	497.9
Lease operating expense	0	0
Natural gas, oil and NGL transportation and other handling costs	0	0
Gathering, processing and other	1.7	1.6
General and administrative	1.8	1.2
Production and property taxes	0.3	0.5
Depreciation, depletion and amortization	2.7	2.5
Other operating expenses	0	0
Total operating expenses	349.3	503.7
Net gain (loss) from asset sales	(2.7)	0
Operating income (loss)	(6.2)	4.1
Realized and unrealized gains (losses) on derivative contracts	0.7	(2.4)
Interest and other income (expense)	48.0	48.8
Interest expense	(36.7)	(41.8)
Income (loss) before income taxes	5.8	8.7
Income taxes	2.1	(1.1)
Income from continuing operations		7.6
NET INCOME (LOSS)		0
Net income (loss)	3.7	7.6
Assets		225.3
QEP Marketing and Other [Member] | Unaffiliated customers [Member]
Revenues
Total Revenues	138.3	204.3
QEP Marketing and Other [Member] | Affiliated customers [Member]
Revenues
Total Revenues	207.5	303.5
Elimination [Member]
Revenues
Total Revenues	(207.5)	(303.5)
Operating expenses
Purchased gas and oil expense	(204.6)	(298.0)
Lease operating expense	0	0
Natural gas, oil and NGL transportation and other handling costs	(2.3)	(4.6)
Gathering, processing and other	0	0
General and administrative	(0.6)	(0.9)
Production and property taxes	0	0
Depreciation, depletion and amortization	0	0
Other operating expenses	0	0
Total operating expenses	(207.5)	(303.5)
Net gain (loss) from asset sales	0	0
Operating income (loss)	0	0
Realized and unrealized gains (losses) on derivative contracts	0	0
Interest and other income (expense)	(47.1)	(48.8)
Interest expense	47.1	48.8
Income (loss) before income taxes	0	0
Income taxes	0	0
Income from continuing operations		0
NET INCOME (LOSS)		0
Net income (loss)	0	0
Assets		0
Elimination [Member] | Unaffiliated customers [Member]
Revenues
Total Revenues	0	0
Elimination [Member] | Affiliated customers [Member]
Revenues
Total Revenues	(207.5)	(303.5)
Discontinued Operations [Member]
Revenues
Total Revenues		0
Operating expenses
Purchased gas and oil expense		0
Lease operating expense		0
Natural gas, oil and NGL transportation and other handling costs		0
Gathering, processing and other		0
General and administrative		0
Production and property taxes		0
Depreciation, depletion and amortization		0
Other operating expenses		0
Total operating expenses		0
Net gain (loss) from asset sales		0
Operating income (loss)		0
Realized and unrealized gains (losses) on derivative contracts		0
Interest and other income (expense)		0
Interest expense		0
Income (loss) before income taxes		0
Income taxes		0
Income from continuing operations		0
NET INCOME (LOSS)		27.0
Net income (loss)		27.0
Assets		1,306.2
Discontinued Operations [Member] | Unaffiliated customers [Member]
Revenues
Total Revenues		0
Discontinued Operations [Member] | Affiliated customers [Member]
Revenues
Total Revenues		$ 0