Fair-Value Measurements (Summary Of Valuation Of Financial Instruments At Fair-Value) (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Fair Value, Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	$ 402,306	$ 388,053
Current marketable securities	11,230
Other marketable securities	5,568	6,039
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	89,532	118,763
Current marketable securities
Other marketable securities
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	312,774	269,290
Current marketable securities	11,230
Other marketable securities
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents
Current marketable securities
Other marketable securities	$ 5,568	$ 6,039

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Company may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months.

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Trading Securities which consist of all investments in certain debt and equity securities that are bought and held principally for the purpose of selling them in the near term (thus held for only a short period of time) or for which an entity has elected the fair value option. Trading generally reflects active and frequent buying and selling, and trading securities are generally used with the objective of generating profits on short-term differences in price, but this category of investments may also include items which are not intended to be sold in the near term or for which the fair value option has been elected.

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