Fair Value Measurements - Nonrecurring (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net Book Value Prior To Impairment	$ 0
Non-cash impairment of oil and gas properties	0
Fair Value, Measurements, Nonrecurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Oil and Gas Property, Successful Effort Method, Net	0
Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Oil and Gas Property, Successful Effort Method, Net	0
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Oil and Gas Property, Successful Effort Method, Net	$ 0
Uinta Basin [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net Book Value Prior To Impairment		$ 144,532
Non-cash impairment of oil and gas properties		37,945
Uinta Basin [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Oil and Gas Property, Successful Effort Method, Net		0
Uinta Basin [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Oil and Gas Property, Successful Effort Method, Net		0
Uinta Basin [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Oil and Gas Property, Successful Effort Method, Net		106,587
DJ Basin, Unproved [Domain]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net Book Value Prior To Impairment		20,887
Non-cash impairment of oil and gas properties		2,055
DJ Basin, Unproved [Domain] | Fair Value, Measurements, Nonrecurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Oil and Gas Property, Successful Effort Method, Net		0
DJ Basin, Unproved [Domain] | Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Oil and Gas Property, Successful Effort Method, Net		0
DJ Basin, Unproved [Domain] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Oil and Gas Property, Successful Effort Method, Net		18,832
Piceance Basin, Unproved [Domain]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net Book Value Prior To Impairment		9,098
Non-cash impairment of oil and gas properties		9,098
Piceance Basin, Unproved [Domain] | Fair Value, Measurements, Nonrecurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Oil and Gas Property, Successful Effort Method, Net		0
Piceance Basin, Unproved [Domain] | Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Oil and Gas Property, Successful Effort Method, Net		0
Piceance Basin, Unproved [Domain] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Oil and Gas Property, Successful Effort Method, Net		$ 0