Derivative Financial Instruments (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Summary of location and aggregate fair value of all derivative financial instruments recorded in the consolidated statements of operations
Realized (loss) gain on derivatives	$ (4,321)	$ 9,286	$ 77,094
Unrealized gain (loss) on derivatives	9,715	(41,238)	(39,265)
Revenues [Member]
Summary of location and aggregate fair value of all derivative financial instruments recorded in the consolidated statements of operations
Realized (loss) gain on derivatives	(4,321)	9,286	77,094
Unrealized gain (loss) on derivatives	9,715	(41,238)	(39,265)
Total	5,394	(31,952)	37,829
Oil [Member] | Revenues [Member]
Summary of location and aggregate fair value of all derivative financial instruments recorded in the consolidated statements of operations
Realized (loss) gain on derivatives	(3,657)	5,851	62,259
Unrealized gain (loss) on derivatives	2,638	(18,969)	(31,897)
Natural Gas [Member] | Revenues [Member]
Summary of location and aggregate fair value of all derivative financial instruments recorded in the consolidated statements of operations
Realized (loss) gain on derivatives	(608)	3,435	12,653
Unrealized gain (loss) on derivatives	7,077	(22,269)	(5,440)
NGL's [Member] | Revenues [Member]
Summary of location and aggregate fair value of all derivative financial instruments recorded in the consolidated statements of operations
Realized (loss) gain on derivatives	(56)	0	2,182
Unrealized gain (loss) on derivatives	$ 0	$ 0	$ (1,928)