Derivatives and Risk Management - Schedules of Fair Values and Locations of Derivative Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Gross Asset	$ 35,669	$ 43,222
Gross Liability	(97,348)	(82,203)
Collateral Netted	4,477	10,148
Net Asset (Liability) on Balance Sheet	(57,202)	(28,833)
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Collateral Netted	10,100	6,770
Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Collateral Netted	(5,623)	3,378
Other Current Liabilities [Member] \| Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	7
Gross Liability	(52)
Collateral Netted	0
Net Asset (Liability) on Balance Sheet	(45)
Other Current Liabilities [Member] \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset		238
Gross Liability		(9,379)
Collateral Netted		1,316
Net Asset (Liability) on Balance Sheet		(7,825)
Other Current Liabilities [Member] \| Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	136	34,760
Gross Liability	(4,534)	(41,241)
Collateral Netted	0	3,378
Net Asset (Liability) on Balance Sheet	(4,398)	(3,103)
Other Current Assets [Member] \| Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Gross Asset		97
Gross Liability		0
Collateral Netted		0
Net Asset (Liability) on Balance Sheet		97
Other Current Assets [Member] \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset		589
Gross Liability		0
Collateral Netted		0
Net Asset (Liability) on Balance Sheet		589
Other Current Assets [Member] \| Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	27,305	416
Gross Liability	(22,188)	(245)
Collateral Netted	(4,551)	0
Net Asset (Liability) on Balance Sheet	566	171
Other Property And Investments Net And Other Non-current Assets [Member] \| Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	8,221	6,369
Gross Liability	(3,976)	(5,446)
Collateral Netted	(1,072)	0
Net Asset (Liability) on Balance Sheet	3,173	923
Other Noncurrent Liabilities [Member] \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	0	725
Gross Liability	(66,598)	(24,677)
Collateral Netted	10,100	5,454
Net Asset (Liability) on Balance Sheet	$ (56,498)	(18,498)
Other Noncurrent Liabilities [Member] \| Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset		28
Gross Liability		(1,215)
Collateral Netted		0
Net Asset (Liability) on Balance Sheet		$ (1,187)

Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

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