Derivative Financial Instruments (Schedule Of Fair Values Of Derivative Financial Instruments) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019		Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	$ 14,515		$ 9,977
Liability Derivatives, Fair Value	7,771		7,854
Net unrealized losses on cash flow hedges	100
Unrealized Gain (Loss) on Commodity Contracts	3,400		16,300
Derivative Financial Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	14,515	[1]	9,976	[2]
Liability Derivatives, Fair Value	7,771		7,852
Other Assets [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value			1
Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value
Liability Derivatives, Fair Value			$ 2

[1] At December 31, 2019, derivative financial instruments, as reflected on the balance sheet, includes net unrealized gains on exchange traded futures and options contracts of $3.4 million, which include $0.1 million of net unrealized gains on derivative financial instruments designated as cash flow hedging instruments.

[2] At December 31, 2018, derivative financial instruments, as reflected on the balance sheet, includes net unrealized gains on exchange traded futures and options contracts of $16.3 million.