We estimate fair value at a price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants in the principal market for the asset or liability. The valuation techniques require inputs that the business categorizes using a three-level hierarchy, from highest to lowest level of observable inputs, as follows: unadjusted quoted prices for identical assets or liabilities in active markets ("Level 1"); direct or indirect observable inputs, including quoted prices or other market data, for similar assets or liabilities in active markets or identical assets or liabilities in less active markets ("Level 2"); and unobservable inputs that require significant judgment for which there is little or no market data ("Level 3"). When multiple input levels are required for a valuation, we categorize the entire fair value measurement according to the lowest level of input that is significant to the measurement, even though we may have also utilized significant inputs that are more readily observable.

The period-end carrying amounts of cash and cash equivalents, receivables, accounts payable and accrued liabilities approximate fair value because of the short maturity of these instruments. The period-end carrying amount of short-term marketable securities also approximates fair value and consists of available-for-sale debt securities. Unrealized gains and losses are reported net of tax as a component of AOCI in the accompanying condensed consolidated statements of financial position. There were no allowances for credit losses for the nine months ended September 30, 2020 and 2019. The carrying amount of total debt was $976 million and $980 million, and the estimated fair value was $1,005 million and $1,031 million as of September 30, 2020 and December 31, 2019, respectively. The fair value of our debt is estimated based on available market prices for the same or similar instruments that are considered significant other observable inputs (Level 2) within the fair value hierarchy. The fair values presented reflect the amounts that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (exit price). The fair value estimates presented in this report are based on information available to us as of September 30, 2020 and December 31, 2019.

We value our interest rate swap contract using a forward interest rate curve obtained from a third-party market data provider. The fair value of the contract is the sum of the expected future settlements between the contract counterparties, discounted to present value. The expected future settlements are determined by comparing the contract interest rate to the expected forward interest rate as of each settlement date and applying the difference between the two rates to the notional amount of debt in the interest rate swap contract.

We have not changed our valuation techniques for measuring the fair value of any financial assets and liabilities during the year. Transfers between levels, if any, are recognized at the end of the reporting period. There were no transfers between levels during the nine months ended September 30, 2020 and 2019.

The carrying amount and estimated fair value of our financial instruments that are recorded at fair value on a recurring basis for the periods presented are as follows:



				Estimated Fair Value Measurements
(In millions)	Statement of Financial ‎Position Location	Carrying ‎Value		Quoted ‎Prices ‎In Active ‎Markets ‎(Level 1)		Significant ‎Other ‎Observable ‎Inputs ‎(Level 2)		Significant ‎Unobservable ‎Inputs ‎(Level 3)
As of September 30, 2020:
Financial Liabilities:
Interest rate swap contract	Other accrued liabilities	$	10	$	—	$	10	$	—
	Other long-term obligations		36		—		36		—
Total financial liabilities		$	47	$	—	$	47	$	—

As of December 31, 2019:
Financial Assets:
Investments in marketable securities	Marketable securities	$	7	$	7	$	—	$	—
Total financial assets		$	7	$	7	$	—	$	—
Financial Liabilities:
Interest rate swap contract	Other accrued liabilities	$	5	$	—	$	5	$	—
	Other long-term obligations		22		—		22		—
Total financial liabilities		$	27	$	—	$	27	$	—