Cash and Cash Equivalents and Short-term Investments (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
Cash and cash equivalents, short-term and long-term investments and other receivables
Cash and cash equivalents	$ 564,888	$ 524,922	$ 354,022	$ 398,575
Short-term investments:
Trading equity securities		52,705
Available-for-sale equity securities	97,118	174,610
Available-for-sale debt securities	28,474	25,967
Total short-term investments	$ 125,592	$ 253,282

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

Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, 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. Excludes cash and cash equivalents within disposal group and discontinued operation.

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- 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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