Basis of Presentation Restricted Cash (Details) - USD ($) $ in Millions		Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents		$ 0.0	$ 0.0	$ 178.8
Restricted cash(1)	[1]	26.1		22.4
Total cash, cash equivalents and restricted cash shown in the Condensed Consolidated Statements of Cash Flows		26.1	$ 23.4	201.2	$ 465.4
Long-term [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash(1)		$ 26.1		$ 22.4

[1] As of June 30, 2018, the restricted cash balance consisted of $26.1 million included within "Other noncurrent assets" on the Condensed Consolidated Balance Sheet. As of June 30, 2017, the restricted cash balance consisted of $22.4 million included within "Other noncurrent assets" 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.