Operations by Line of Business (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenues
Total Revenues	$ 704.9	$ 542.4	$ 499.3	$ 603.2	$ 853.3	$ 879.9	$ 808.1	$ 617.9	$ 2,349.8	$ 3,159.2	$ 2,300.6
Operating expenses
Purchased gas, oil and NGL expense									655.6	1,077.1	589.3
Lease operating expense									172.3	145.2	125.0
Natural gas, oil and NGL transportation and other handling costs									148.9	102.2	54.2
Gathering, processing and other									88.0	107.3	83.2
General and administrative									266.6	123.2	107.2
Separation costs									0	0	13.5
Production and property taxes									103.4	105.4	82.5
Results of Operations, Depreciation, Depletion, Amortization and Accretion									904.9	765.4	643.4
Other Expenses									144.6	228.9	69.1
Operating Expenses									2,484.3	2,654.7	1,767.4
Gain (Loss) on Sale of Property Plant Equipment									1.2	1.4	12.1
OPERATING (LOSS) INCOME	(114.7)	(12.6)	(55.5)	49.5	16.5	183.4	168.9	137.1	(133.3)	505.9	545.3
Realized and unrealized gains (losses) on derivative contracts									441.9	0	0
Interest and other income									6.6	4.1	2.3
Income from unconsolidated affiliates									6.8	5.5	3.0
Loss from early extinguishment of debt									(0.6)	(0.7)	(13.3)
Interest expense									(122.9)	(90.0)	(84.4)
Income (loss) before income taxes	(42.1)	(4.4)	0.3	244.7	(0.9)	161.5	147.7	116.5	198.5	424.8	452.9
Income taxes									(66.5)	(154.4)	(167.0)
Income from Continuing Operations									132.0	270.4	285.9
Discontinued operations, net of income tax									0	0	43.2
NET INCOME									132.0	270.4	329.1
Net income attributable to noncontrolling interest									(3.7)	(3.2)	(2.9)
NET INCOME ATTRIBUTABLE TO QEP	(23.1)	(3.1)	(0.7)	155.2	(0.3)	101.5	92.8	73.2	128.3	267.2	326.2
Assets	9,108.5				7,442.7				9,108.5	7,442.7	6,785.3
Equity Method Investments	41.2				42.2				41.2	42.2	44.5
Cash capital expenditures									2,799.7	1,431.1	1,469.0
Accrued capital expenditures									2,888.2	1,445.8	1,485.9
Goodwill	59.5				59.5				59.5	59.5	59.6
Unaffiliated customers [Member]
Revenues
Total Revenues									2,349.8	3,159.2	2,300.6
Affiliated customers [Member]
Revenues
Total Revenues									0	0	0
QEP Energy [Member]
Revenues
Total Revenues									1,615.4	2,213.2	1,456.3
Operating expenses
Purchased gas, oil and NGL expense									224.7	506.4	0
Lease operating expense									175.8	148.2	127.3
Natural gas, oil and NGL transportation and other handling costs									228.1	186.0	125.5
Gathering, processing and other									0	0	0
General and administrative									237.6	98.4	78.0
Separation costs											0
Production and property taxes									97.2	99.1	77.8
Results of Operations, Depreciation, Depletion, Amortization and Accretion									838.0	707.2	592.5
Other Expenses									144.6	228.9	69.1
Operating Expenses									1,946.0	1,974.2	1,070.2
Gain (Loss) on Sale of Property Plant Equipment									1.2	1.4	13.7
OPERATING (LOSS) INCOME									(329.4)	240.4	399.8
Realized and unrealized gains (losses) on derivative contracts									434.9
Interest and other income									6.2	4.0	2.1
Income from unconsolidated affiliates									0.1	0.1	0.2
Loss from early extinguishment of debt									0	0	0
Interest expense									(116.8)	(81.9)	(78.5)
Income (loss) before income taxes									(5.0)	162.6	323.6
Income taxes									4.3	(57.9)	(119.7)
Income from Continuing Operations											203.9
Discontinued operations, net of income tax											0
NET INCOME									(0.7)	104.7	203.9
Net income attributable to noncontrolling interest									0	0	0
NET INCOME ATTRIBUTABLE TO QEP									(0.7)	104.7	203.9
Assets	7,436.5				5,815.7				7,436.5	5,815.7	5,391.9
Equity Method Investments	0				0				0	0	0
Cash capital expenditures									2,621.1	1,295.5	1,205.0
Accrued capital expenditures									2,702.4	1,338.7	1,215.8
Goodwill	59.5				59.5				59.5	59.5	59.6
QEP Energy [Member] | Unaffiliated customers [Member]
Revenues
Total Revenues									1,615.4	2,213.2	1,456.3
QEP Energy [Member] | Affiliated customers [Member]
Revenues
Total Revenues									0	0	0
QEP Field Services [Member]
Revenues
Total Revenues									439.2	465.5	319.2
Operating expenses
Purchased gas, oil and NGL expense									12.1	0	0
Lease operating expense									0	0	0
Natural gas, oil and NGL transportation and other handling costs									33.6	9.3	0
Gathering, processing and other									86.8	106.0	82.1
General and administrative									34.7	29.2	31.6
Separation costs											0
Production and property taxes									6.0	6.1	4.4
Results of Operations, Depreciation, Depletion, Amortization and Accretion									63.2	55.7	48.9
Other Expenses									0	0	0
Operating Expenses									236.4	206.3	167.0
Gain (Loss) on Sale of Property Plant Equipment									0	0	(1.6)
OPERATING (LOSS) INCOME									202.8	259.2	150.6
Realized and unrealized gains (losses) on derivative contracts									8.4
Interest and other income									0.2	0.1	0.1
Income from unconsolidated affiliates									6.7	5.4	2.8
Loss from early extinguishment of debt									0	0	0
Interest expense									(13.6)	(13.6)	(7.6)
Income (loss) before income taxes									204.5	251.1	145.9
Income taxes									(71.8)	(93.4)	(51.9)
Income from Continuing Operations											94.0
Discontinued operations, net of income tax											0
NET INCOME									132.7	157.7	94.0
Net income attributable to noncontrolling interest									(3.7)	(3.2)	(2.9)
NET INCOME ATTRIBUTABLE TO QEP									129.0	154.5	91.1
Assets	1,399.7				1,312.7				1,399.7	1,312.7	1,197.5
Equity Method Investments	41.2				42.2				41.2	42.2	44.5
Cash capital expenditures									164.0	130.1	262.1
Accrued capital expenditures									171.2	101.6	268.2
Goodwill	0				0				0	0	0
QEP Field Services [Member] | Unaffiliated customers [Member]
Revenues
Total Revenues									320.2	369.3	245.5
QEP Field Services [Member] | Affiliated customers [Member]
Revenues
Total Revenues									119.0	96.2	73.7
QEP Marketing and Other [Member]
Revenues
Total Revenues									1,019.9	1,156.9	1,098.5
Operating expenses
Purchased gas, oil and NGL expense									1,021.1	1,144.5	1,082.8
Lease operating expense									0	0	0
Natural gas, oil and NGL transportation and other handling costs									0	0	0
Gathering, processing and other									1.2	1.3	1.1
General and administrative									0.4	2.1	3.9
Separation costs											13.5
Production and property taxes									0.2	0.2	0.3
Results of Operations, Depreciation, Depletion, Amortization and Accretion									3.7	2.5	2.0
Other Expenses									0	0	0
Operating Expenses									1,026.6	1,150.6	1,103.6
Gain (Loss) on Sale of Property Plant Equipment									0	0	0
OPERATING (LOSS) INCOME									(6.7)	6.3	(5.1)
Realized and unrealized gains (losses) on derivative contracts									(1.4)
Interest and other income									132.1	98.7	87.2
Income from unconsolidated affiliates									0	0	0
Loss from early extinguishment of debt									(0.6)	(0.7)	(13.3)
Interest expense									(124.4)	(93.2)	(85.4)
Income (loss) before income taxes									(1.0)	11.1	(16.6)
Income taxes									1.0	(3.1)	4.6
Income from Continuing Operations											(12.0)
Discontinued operations, net of income tax											(43.2)
NET INCOME									0	8.0	31.2
Net income attributable to noncontrolling interest									0	0	0
NET INCOME ATTRIBUTABLE TO QEP									0	8.0	31.2
Assets	272.3				314.3				272.3	314.3	195.9
Equity Method Investments	0				0				0	0	0
Cash capital expenditures									14.6	5.5	1.9
Accrued capital expenditures									14.6	5.5	1.9
Goodwill	0				0				0	0	0
QEP Marketing and Other [Member] | Unaffiliated customers [Member]
Revenues
Total Revenues									414.2	576.7	598.8
QEP Marketing and Other [Member] | Affiliated customers [Member]
Revenues
Total Revenues									605.7	580.2	499.7
Elimination [Member]
Revenues
Total Revenues									(724.7)	(676.4)	(573.4)
Operating expenses
Purchased gas, oil and NGL expense									(602.3)	(573.8)	(493.5)
Lease operating expense									(3.5)	(3.0)	(2.3)
Natural gas, oil and NGL transportation and other handling costs									(112.8)	(93.1)	(71.3)
Gathering, processing and other									0	0	0
General and administrative									(6.1)	(6.5)	(6.3)
Separation costs											0
Production and property taxes									0	0	0
Results of Operations, Depreciation, Depletion, Amortization and Accretion									0	0	0
Other Expenses									0	0	0
Operating Expenses									(724.7)	(676.4)	(573.4)
Gain (Loss) on Sale of Property Plant Equipment									0	0	0
OPERATING (LOSS) INCOME									0	0	0
Realized and unrealized gains (losses) on derivative contracts									0
Interest and other income									(131.9)	(98.7)	(87.1)
Income from unconsolidated affiliates									0	0	0
Loss from early extinguishment of debt									0	0	0
Interest expense									131.9	98.7	87.1
Income (loss) before income taxes									0	0	0
Income taxes									0	0	0
Income from Continuing Operations											0
Discontinued operations, net of income tax											0
NET INCOME									0	0	0
Net income attributable to noncontrolling interest									0	0	0
NET INCOME ATTRIBUTABLE TO QEP									0	0	0
Assets	0				0				0	0	0
Equity Method Investments	0				0				0	0	0
Cash capital expenditures									0	0	0
Accrued capital expenditures									0	0	0
Goodwill	0				0				0	0	0
Elimination [Member] | Unaffiliated customers [Member]
Revenues
Total Revenues									0	0	0
Elimination [Member] | Affiliated customers [Member]
Revenues
Total Revenues									$ (724.7)	$ (676.4)	$ (573.4)