Basis of Presentation Restricted Cash (Details) - USD ($) $ in Millions		Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents		$ 0.0	$ 0.0	$ 338.4
Restricted cash(1)	[1]	24.5		22.1
Total cash, cash equivalents and restricted cash shown in the Condensed Consolidated Statements of Cash Flows		24.5	$ 23.4	360.5	$ 465.4
Short-term [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash(1)				1.2
Long-term [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash(1)		$ 24.5		$ 20.9

[1] As of March 31, 2018, the restricted cash balance consisted of $24.5 million included within "Other noncurrent assets" on the Condensed Consolidated Balance Sheet. As of March 31, 2017, the restricted cash balance consisted of $20.9 million included within "Other noncurrent assets" and $1.2 million included within "Prepaid expenses" on the Condensed Consolidated Balance Sheet provided within the Quarterly Report on Form 10-Q. QEP's restricted cash is primarily cash deposited into an escrow account related to a title dispute between third parties in the Williston Basin.