Fair Value

The following table reflects the carrying amount and estimated fair value of our debt, excluding total other financing obligations (in millions):



	September 30, 2013				December 31, 2012
	Carrying Amount		Estimated Fair Value		Carrying Amount		Estimated Fair Value
Total debt, excluding total other financing obligations⁽¹⁾	$	475	$	534	$	475	$	561

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(1)	Our other financing obligations were $170 million and $172 million as of September 30, 2013 and December 31, 2012, of which $5 million was reported as "Current portion of debt" on our Consolidated Balance Sheets for each period. For a further discussion of our other financing obligations, see our 2012 Form 10-K.

We separate the fair values of our financial instruments into levels based on our assessment of the availability of observable market data and the significance of non-observable data used to determine the estimated fair value. We estimated the above fair values of debt, excluding total other financing obligations, primarily based on quoted market prices for the same or similar issues, a Level 2 fair value measurement. Our assessment and classification of an instrument within a level can change over time based on the maturity or liquidity of the instrument and this change would be reflected at the end of the period in which the change occurs. During the nine months ended September 30, 2013, there were no changes to the inputs and valuation techniques used to measure fair value of these instruments, or the levels in which they were classified.

As of September 30, 2013 and December 31, 2012, the carrying amounts of cash and cash equivalents, accounts receivable and accounts payable represent their fair values based on the short-term nature of these items. The carrying amount of our affiliate note receivable approximates its fair value due to the note being due on demand and the market-based nature of the interest rate.