Derivative Instruments - Fair Value of Derivative Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Total Current Assets	$ 312,749	$ 247,794
Total Other Assets	258,111	314,096
Total Current Liabilities	49,058	41,466
Total Non-current Liabilities	163,898	115,862
Commodity Swap
Derivative [Line Items]
Total Current Assets	296,834	234,238
Total Other Assets	244,501	288,543
Total Current Liabilities	5,028	345
Total Non-current Liabilities	23,018	9,693
Basis Swap
Derivative [Line Items]
Total Current Assets	15,718	13,556
Total Other Assets	12,396	25,553
Total Current Liabilities	41,069	40,626
Total Non-current Liabilities	130,572	105,445
Interest Rate Swap
Derivative [Line Items]
Total Current Assets	197	0
Total Other Assets	1,214	0
Total Current Liabilities	2,961	495
Total Non-current Liabilities	$ 10,308	$ 724