Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets (Liabilities)
Derivative Liability	$ 15,239	$ 24,954
Derivative, Fair Value, Net	(15,239)
Fair value on a recurring basis [Member]
Assets (Liabilities)
Derivative Liability	1,190	(24,954)
Derivative Assets (Liabilities), at Fair Value, Net	(15,239)
Fair value on a recurring basis [Member] | Oil [Member]
Assets (Liabilities)
Derivative Assets (Liabilities), at Fair Value, Net	(16,429)	(24,954)
Fair value on a recurring basis [Member] | Level 1 [Member]
Assets (Liabilities)
Derivative Liability	0	0
Fair value on a recurring basis [Member] | Level 1 [Member] | Oil [Member]
Assets (Liabilities)
Derivative Assets (Liabilities), at Fair Value, Net	0
Fair value on a recurring basis [Member] | Level 2 [Member]
Assets (Liabilities)
Derivative Liability	1,190	(24,954)
Derivative, Fair Value, Net	(15,239)	(24,954)
Fair value on a recurring basis [Member] | Level 2 [Member] | Oil [Member]
Assets (Liabilities)
Derivative Assets (Liabilities), at Fair Value, Net	(16,429)
Fair value on a recurring basis [Member] | Level 3 [Member]
Assets (Liabilities)
Derivative Liability	0	$ 0
Fair value on a recurring basis [Member] | Level 3 [Member] | Oil [Member]
Assets (Liabilities)
Derivative Assets (Liabilities), at Fair Value, Net	$ 0