Summary of Significant Accounting Policies (Details 7) (Fair value measured on recurring basis, USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Total Carrying Value
Assets and liabilities carried at fair value measured on a recurring basis
Money market funds	$ 68,028	$ 68,800
Time deposits	141,695	149,829
Trading securities	11,437	11,071
Derivative assets	5,538
Derivative liabilities	1,709	1,522
Quoted prices in active markets (Level 1)
Assets and liabilities carried at fair value measured on a recurring basis
Trading securities	10,923	10,525
Significant other observable inputs (Level 2)
Assets and liabilities carried at fair value measured on a recurring basis
Money market funds	68,028	68,800
Time deposits	141,695	149,829
Trading securities	514	546
Derivative assets	5,538
Derivative liabilities	$ 1,709	$ 1,522

Investment in short-term money-market instruments (such as commercial paper, banker's acceptances, repurchase agreements, government securities, certificates of deposit, and so forth) which are highly liquid (that is, readily convertible to known amounts of cash) and so near their maturity that they present an insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify as cash equivalents by definition. Original maturity means an 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.

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Any certificate of deposit or savings account held by a bank or other financial institution for a short-term specified period of time. Because of their short-term, time deposits are considered highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant 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.

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- Definition

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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