Cash and Cash Equivalents and Short-term Investments (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Dec. 31, 2010
Cash and cash equivalents, short-term and long-term investments and other receivables
Cash and cash equivalents	$ 354,022	$ 398,575	$ 569,736	$ 641,702
Short-term investments:
Trading equity securities	17,638	11,600
Available-for-sale equity securities	81,227	71,433
Available-for-sale debt securities	41,085	57,881
Total short-term investments	$ 139,950	$ 140,914

Total of debt securities categorized neither as held-to-maturity nor trading which are intended be sold or mature within one year from the balance sheet date or the normal operating cycle, whichever is longer.

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- Definition

Equity securities categorized neither as held-to-maturity nor trading which are intended be sold within one year from the balance sheet date or the normal operating cycle, whichever is longer.

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- Definition

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 Entity 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. Compensating balance arrangements that do not legally restrict the withdrawal or usage of cash amounts may be reported as Cash and Cash Equivalents, while legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or company statements of intention with regard to particular deposits are not generally reported as cash and cash equivalents. Includes cash and cash equivalents associated with the entity's continuing operations. Excludes cash and cash equivalents associated with the disposal group (and discontinued operation).

+ References

+ Details

- Definition

Total common and preferred stock (which is neither mandatorily redeemable nor redeemable at the option of the holder) 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, usually less than one year or the normal operating cycle, whichever is longer) or for equity securities formerly categorized as available-for-sale or held-to-maturity which the entity held as of the date it opted to account for such securities at fair value. An enterprise may also categorize such a security as trading without the intent to sell it in the near term assuming the decision to categorize the security as trading occurred at acquisition.

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