Derivative Instruments - Fair Value of Derivative Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Commodity Swaps
Asset Derivative Instruments
Prepaid Expense	$ 172,836	$ 28,612
Other Assets	254,967	164,310
Total Asset	427,803	192,922
Liability Derivative Instruments
Other Accrued Liabilities	1,389	34,640
Other Liabilities	17,440	52,011
Total Liability	18,829	86,651
Basis Swap
Asset Derivative Instruments
Prepaid Expense	25,420	11,628
Other Assets	20,925	48,788
Total Asset	46,345	60,416
Liability Derivative Instruments
Other Accrued Liabilities	43,437	27,021
Other Liabilities	98,638	40,210
Total Liability	$ 142,075	$ 67,231