Segment Information - Reconciliation of Segment Information, Revenue and Other Operating Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue, Major Customer [Line Items]
Gain on Commodity Derivative Instruments	$ (63,303)	$ 221,581	$ 51,839	$ 26,205
Other Operating Income	3,753	2,923	8,711	6,120
Total Revenue	148,841	605,032	565,200	883,463
Operating Segments
Revenue, Major Customer [Line Items]
Total Segment Revenue from Contracts with External Customers	$ 208,391	$ 380,528	$ 504,650	$ 851,138