Income Taxes Reconciliation of Statutory Federal Income Tax Rate and Effective Tax Rate (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Investments, Owned, Federal Income Tax Note [Line Items]
Federal income tax rate	21.00%		35.00%
Valuation allowance	$ 36.2
Operating Loss Carryforwards					$ 75.7
Alternative minimum tax	$ (148.4)				126.0
Deferred Tax Assets, Tax Credit Carryforwards					$ 50.3
Federal income taxes statutory rate	21.00%		35.00%		35.00%
Increase (decrease) in rate as a result of:
State income taxes, net of federal income tax benefit(1)	(0.70%)		(40.10%)	[1]	2.40%
Federal rate change(2)	0.00%		741.30%	[2]	0.00%
State rate change	0.00%		2.10%		(1.10%)
Permanent adjustments	(0.10%)		(0.40%)		0.00%
Return to provision adjustment	(0.10%)		(0.70%)		0.00%
Uncertain tax provision (federal rate change)	0.00%		(7.70%)		0.00%
AMT Credit Reclass due to NOL Carryback(3)	3.80%	[3]	(1.80%)		0.00%
Effective income tax rate	23.90%		727.70%		36.30%

[1] State income taxes changed significantly from prior years mainly due to the change in valuation allowance recorded during 2017 of $36.2 million.

[2] The Tax Legislation changed the federal corporate income tax rate from 35% to 21% starting in 2018. The rate change caused the Company to revalue its deferred tax liabilities and assets as of December 31, 2017 from a 35% to 21% federal corporate income tax rate which caused the majority of the change in rate.

[3] In 2018, QEP agreed to an IRS proposed change to the initial treatment of the 2016 carryback of net operating losses. This change resulted in a reduction of available net operating loss carryforwards valued at $75.7 million and an increase in alternative minimum tax (AMT) credit carryforwards of $126.0 million. The net change in value of $50.3 million was recorded in deferred income taxes.