Summary of Significant Accounting Policies Summary of Significant Accounting Policies - Disaggregated Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 212,426		$ 397,448
Realized (loss) gain on derivatives	(2,488)	$ 558	(6,746)	$ (1,661)
Unrealized gain on derivatives	1,429	13,190	11,845	33,821
Total revenue	211,367	$ 129,611	402,547	$ 264,425
Oil revenues
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	166,271		314,430
Natural gas revenues
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	42,748		76,543
Third-party midstream services revenues
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	3,407		6,475
Total revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	212,426		397,448
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	2,600		4,800
Cost of Goods and Services Sold	$ (2,600)		$ (4,800)