Derivative Financial Instruments - Offsetting of Derivative Assets and Liabilities (Details) - Zero Cost Collars [Member] - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Asset Derivatives:
Asset Derivatives, Gross amounts of recognized assets/liabilities	$ 262	$ 1,456
Asset Derivatives, Gross amounts offset in the balance sheets	0
Asset Derivatives, Net amounts of assets/liabilities presented in the balance sheets	262	1,456
Asset Derivatives, Gross amounts not offset in the balance sheets, Financial instruments	0
Asset Derivatives, Gross amounts not offset in the balance sheets, Cash collateral pledged	0	(1,070)
Asset Derivatives, Net amount	262	$ 2,526
Liability Derivatives:
Liability Derivatives, Gross amounts of recognized liabilities	33
Liability Derivatives, Gross amounts offset in the balance sheets	0
Liability Derivatives, Net amounts of liabilities presented in the balance sheets	33
Liability Derivatives, Gross amounts not offset in the balance sheets, Financial instruments	0
Liability Derivatives, Gross amounts not offset in the balance sheets, Cash collateral pledged	0
Liability Derivatives, Net amount after master netting	$ 33