Financial Instruments and Concentrations of Risk Financial Instruments (Policies)

12 Months Ended

Dec. 31, 2017

Financial Instruments Policies [Abstract]

Fair Value Measurement, Policy [Policy Text Block]

“Level 1” measurements are based on inputs consisting of unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities. These include commodity futures contracts that are traded on an exchange.

“Level 2” measurements are based on inputs consisting of market observable and corroborated prices for similar derivative contracts. Assets and liabilities classified as Level 2 include over the counter (“OTC”) traded physical fixed priced purchases and sales forward contracts.

“Level 3” measurements are based on inputs from a pricing service and/or internal valuation models incorporating observable and unobservable market data. These could include commodity derivatives, such as forwards and swaps for which there is not a highly liquid market and therefore are not included in Level 2 above and interest rate swaps for which certain unobservable inputs are used in the valuation.

Financial assets and liabilities are classified based on the lowest level of input that is significant to the fair value measurement. Our assessment of the significance of a particular input to the measurement requires judgment and may affect the valuation of assets and liabilities and their placement within the fair value levels. At December 31, 2017, all of our physical fixed price forward purchases and sales contracts were being accounted for as normal purchases and normal sales.