Restructuring Costs (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Restructuring Cost and Reserve [Line Items]
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments	$ 2.2
Estimated restructuring costs	9.9
Restructuring costs incurred to date	7.0
Increase (Decrease) in Restructuring Liability [Roll Forward]
Number of regional offices created	1
One-time Termination Benefits [Member]
Restructuring Cost and Reserve [Line Items]
Estimated restructuring costs	3.5
Restructuring costs incurred to date	3.0
Employee Relocation [Member]
Restructuring Cost and Reserve [Line Items]
Estimated restructuring costs	5.8
Restructuring costs incurred to date	3.4
Termination of Lease [Member]
Restructuring Cost and Reserve [Line Items]
Estimated restructuring costs	0.6
Restructuring costs incurred to date	0.6
QEP Energy [Member]
Restructuring Cost and Reserve [Line Items]
Estimated restructuring costs	9.3
Restructuring costs incurred to date	6.9
Increase (Decrease) in Restructuring Liability [Roll Forward]
Balance at December 31, 2011	0
Costs paid or otherwise settled	(5.9)
Balance at September 30, 2012	1.0
QEP Energy [Member] | One-time Termination Benefits [Member]
Restructuring Cost and Reserve [Line Items]
Estimated restructuring costs	3.3
Restructuring costs incurred to date	2.9
QEP Energy [Member] | Employee Relocation [Member]
Restructuring Cost and Reserve [Line Items]
Estimated restructuring costs	5.4
Restructuring costs incurred to date	3.4
QEP Energy [Member] | Termination of Lease [Member]
Restructuring Cost and Reserve [Line Items]
Estimated restructuring costs	0.6
Restructuring costs incurred to date	0.6
QEP Field Services [Member]
Restructuring Cost and Reserve [Line Items]
Estimated restructuring costs	0.2
Restructuring costs incurred to date	0
Increase (Decrease) in Restructuring Liability [Roll Forward]
Balance at December 31, 2011	0
Costs paid or otherwise settled	0
Balance at September 30, 2012	0
QEP Field Services [Member] | One-time Termination Benefits [Member]
Restructuring Cost and Reserve [Line Items]
Estimated restructuring costs	0
Restructuring costs incurred to date	0
QEP Field Services [Member] | Employee Relocation [Member]
Restructuring Cost and Reserve [Line Items]
Estimated restructuring costs	0.2
Restructuring costs incurred to date	0
QEP Field Services [Member] | Termination of Lease [Member]
Restructuring Cost and Reserve [Line Items]
Estimated restructuring costs	0
Restructuring costs incurred to date	0
QEP Marketing [Member]
Restructuring Cost and Reserve [Line Items]
Estimated restructuring costs	0.4
Restructuring costs incurred to date	0.1
Increase (Decrease) in Restructuring Liability [Roll Forward]
Balance at December 31, 2011	0
Costs paid or otherwise settled	(0.1)
Balance at September 30, 2012	0
QEP Marketing [Member] | One-time Termination Benefits [Member]
Restructuring Cost and Reserve [Line Items]
Estimated restructuring costs	0.2
Restructuring costs incurred to date	0.1
QEP Marketing [Member] | Employee Relocation [Member]
Restructuring Cost and Reserve [Line Items]
Estimated restructuring costs	0.2
Restructuring costs incurred to date	0
QEP Marketing [Member] | Termination of Lease [Member]
Restructuring Cost and Reserve [Line Items]
Estimated restructuring costs	0
Restructuring costs incurred to date	0
QEP Resources [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs incurred to date	7.0
Increase (Decrease) in Restructuring Liability [Roll Forward]
Balance at December 31, 2011	0
Costs paid or otherwise settled	(6.0)
Balance at September 30, 2012	$ 1.0