Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value of the assets less the liabilities of a derivative or group of derivatives.

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Fixed interest rate related to the interest rate derivative.

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The estimated net amount of unrealized gains or losses on foreign currency cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

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Amount before accretion (amortization) of purchase discount (premium) of interest income and dividend income on nonoperating securities.

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Financial Instruments and Risk Management (Narrative) (Details) mmbtus in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($) mmbtus	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) mmbtus	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) mmbtus
Derivative [Line Items]
Foreign currency cash flow hedges losses expected to be recognized in the next 12 months	$ 600,000		$ 600,000
Level 1 to level 2 transfers	0		0		$ 0
Currency Swap
Derivative [Line Items]
Derivative, notional amount		$ 166,200,000		$ 166,200,000
Derivative, fair value, net	7,600,000		7,600,000		3,000,000.0
Interest and dividend	500,000	$ 600,000	1,300,000	$ 600,000
Currency Swap \| US Dollar Denominated
Derivative [Line Items]
Derivative, fixed interest rate		3.79%		3.79%
Currency Swap \| Eurodollar
Derivative [Line Items]
Derivative, fixed interest rate		1.35%		1.35%
Currency exchange contracts
Derivative [Line Items]
Derivative, notional amount	10,200,000		10,200,000
Derivative asset	100,000		100,000		0
Commodity hedging
Derivative [Line Items]
Derivative, fair value, net	$ (300,000)		$ (300,000)		$ (500,000)
Commodity hedging \| Swap
Derivative [Line Items]
Derivative, nonmonetary notional amount \| mmbtus	1.4		1.4
Commodity hedging \| Zero Cost Collar
Derivative [Line Items]
Derivative, nonmonetary notional amount \| mmbtus					0.6
Interest rate swap contracts
Derivative [Line Items]
Derivative, notional amount	$ 166,200,000		$ 166,200,000
Derivative, fair value, net	$ (10,400,000)		$ (10,400,000)		$ (3,900,000)