Derivative instruments, consisting of commodity contracts, were recorded at fair value in our condensed consolidated balance sheets and consisted of a liability of $1 million, recorded in accrued and other current liabilities, and an asset of $1 million, recorded in other current assets, as of June 30, 2020 and December 31, 2019, respectively.

Our commodity contracts are primarily commodity swaps and are all Level 2 financial assets and liabilities. Commodity derivatives are valued using an income approach based on the observable market commodity index prices less the contract rate multiplied by the notional amount or based on pricing models that rely on market observable inputs such as commodity prices. Our calculation of the fair value of these financial instruments takes into consideration the risk of non-performance, including counterparty credit risk. The majority of our derivative contracts do not have a legal right of set-off. We manage the credit risk in connection with our derivatives by limiting the amount of exposure with each counterparty and monitoring the financial condition of our counterparties.

For the three and six months ended June 30, 2020, we recognized an unrealized gain of $3 million and an unrealized loss of $1 million, respectively, compared to unrealized gains of $1 million and $8 million in the comparable prior year periods, in cost of sales in the condensed consolidated statements of income.

The following table provides the detail of outstanding commodity derivative contracts as of June 30, 2020:

Type

Unit of measure

Contracted

volume

Contracted

price range

Contracted date

of maturity

Benzene swaps

U.S. liquid gallon

924,809

$1.09-$2.50

Aug 2020 - Nov 2020

Diesel swaps

U.S. liquid gallon

3,035,859

$2.30-$3.16

Jul 2020 - Jun 2021