Fair Value of Financial Instruments	6 Months Ended
Fair Value of Financial Instruments	Jun. 30, 2011
Fair Value of Financial Instruments [Abstract]
Fair Value of Financial Instruments	Note 9. Fair Value of Financial Instruments At June 30, 2011, we held $451 million of non-cash equivalents in United States Treasury securities with maturities that extend through February 2012. These securities are accounted for as available-for-sale and recorded at fair value, based on quoted market prices, in "Investments in marketable securities" on our condensed consolidated balance sheets. The carrying amount of cash and equivalents, investments in marketable securities, receivables, and accounts payable, as reflected in the condensed consolidated balance sheets, approximates fair value due to the short maturities of these instruments. We have no financial instruments measured at fair value using unobservable inputs. The fair value of our long-term debt was $4.6 billion as of both June 30, 2011 and December 31, 2010, which differs from the carrying amount of $3.8 billion as of both June 30, 2011 and December 31, 2010, on our condensed consolidated balance sheets. The fair value of our long-term debt was calculated using either quoted market prices or significant observable inputs for similar liabilities for the respective periods. We maintain an interest rate management strategy that is intended to mitigate the exposure to changes in interest rates in the aggregate for our investment portfolio. We utilize interest rate swaps to effectively convert a portion of our fixed rate debt to floating rates. The fair value of the swap agreements was not material at June 30, 2011. See Note 4 for further discussion of our interest rate swaps. At June 30, 2011, we had fixed rate debt aggregating $2.8 billion and variable rate debt aggregating $1 billion, after taking into account the effects of the interest rate swaps.

This item represents the complete disclosure regarding the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments, assets, and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the Company is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risk is are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

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