Derivative Financial Instruments (Narrative) (Details)	Mar. 31, 2020 USD ($) bbl	Dec. 31, 2019 USD ($)
Derivative [Line Items]
Commodity derivatives deposits	$ 50,345,000	$ 0
Good Faith and Margin Deposits with Broker-Dealers	0	27,415,000
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months	$ (3,200,000)
Energy Related Derivative [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount \| bbl	30,000
Derivative Liability	$ 18,500,000	$ 17,300,000
Future Debt Issuance 2021 [Member] \| Cash Flow Hedging [Member] \| Interest Rate Contract [Member]
Derivative [Line Items]
Derivative, Notional Amount	100,000,000.0
Derivative Liability, Fair Value, Gross Liability	$ 11,900,000

The current portion, due within one year or one operating cycle, if longer, of deposits held other than customer deposits.

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Amount of right to receive cash and securities on deposit with broker-dealers to demonstrate an intention to complete a purchase (good faith deposit) and collateral deposited by counterparty to cover the credit risk assumed (margin deposit).

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The estimated net amount of unrealized gains or losses on interest rate cash flow hedges as of the balance sheet date expected to be reclassified to earnings within the next twelve months.

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