Fair Value Measurements (Details) - USD ($) shares in Millions			12 Months Ended
		Dec. 21, 2016	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Financial assets and liabilities measured at fair value on a recurring basis
Impairment of Long-Lived Assets Held-for-use			$ 0		$ 0		$ 49,369,000
Impairment of Proved Oil and Gas Properties			3,806,000		354,614,000		$ 468,679,000
Assets:
Derivatives			104,628,000		122,096,000
Liabilities [Abstract]
Derivative Liability, Fair Value, Gross Liability			243,984,000		213,804,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Assets:
Derivatives	[1]		0
Liabilities [Abstract]
Derivative Liability, Fair Value, Gross Liability	[1]		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Assets:
Derivatives	[1]		0
Liabilities [Abstract]
Derivative Liability, Fair Value, Gross Liability	[1]		0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member]
Assets:
Total property and equipment, net	[2]				0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member]
Assets:
Total property and equipment, net	[2]				0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Assets:
Total property and equipment, net	[2]				88,205,000
Disposal group, held-for-sale, not discontinued operations [Member] | Divide County disposal group [Member]
Financial assets and liabilities measured at fair value on a recurring basis
Impairment of Proved Oil and Gas Properties			526,500,000
QStar Acquisition 2016 [Member]
Liabilities [Abstract]
Private issuance of Common Stock for an acquisition		13.4
Not Designated as Hedging Instrument [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Assets:
Derivatives	[3]				0
Liabilities [Abstract]
Derivative Liability, Fair Value, Gross Liability	[3]				0
Not Designated as Hedging Instrument [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Assets:
Derivatives			104,628,000	[1]	122,096,000	[3]
Liabilities [Abstract]
Derivative Liability, Fair Value, Gross Liability			$ 243,984,000	[1]	213,804,000	[3]
Not Designated as Hedging Instrument [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Assets:
Derivatives	[3]				0
Liabilities [Abstract]
Derivative Liability, Fair Value, Gross Liability	[3]				$ 0

[1] This represents a financial asset or liability that is measured at fair value on a recurring basis.

[2] This represents a non-financial asset that is measured at fair value on a nonrecurring basis.

[3] This represents a financial asset or liability that is measured at fair value on a recurring basis.