Investments - Schedule of Fair Value of Available for Sale of Investments (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Schedule Of Available For Sale And Trading Securities [Line Items]
Fair value of short-term available-for-sale investments	$ 330,821	$ 326,862
Fair value of long-term available-for-sale investments	10,157	12,158
Fair value of short-term investments	331,634	327,653
Time deposits [Member]
Schedule Of Available For Sale And Trading Securities [Line Items]
Fair value of short-term available-for-sale investments		52
Fair value of long-term available-for-sale investments	53
Bankers' acceptance drafts [Member]
Schedule Of Available For Sale And Trading Securities [Line Items]
Fair value of short-term available-for-sale investments	93	242
U.S. treasury obligations [Member]
Schedule Of Available For Sale And Trading Securities [Line Items]
Fair value of short-term available-for-sale investments, U.S. agency obligations	13,042	13,054
U.S. agency obligations [Member]
Schedule Of Available For Sale And Trading Securities [Line Items]
Fair value of short-term available-for-sale investments, U.S. agency obligations	317,686	313,514
Fair value of long-term available-for-sale investments	10,104	12,158
Mutual funds [Member]
Schedule Of Available For Sale And Trading Securities [Line Items]
Fair value of short-term investments, mutual funds	$ 813	$ 791

Amount of investment in debt and equity securities categorized neither as trading securities nor held-to-maturity securities and intended be sold or mature one year or operating cycle, if longer.

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+ Details

- Definition

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.

+ References

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

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- Definition

Investments in debt and equity securities which are categorized neither as held-to-maturity nor trading and which are intended to be sold or mature more than one year from the balance sheet date or operating cycle, if longer. Such securities are reported at fair value; unrealized gains (losses) related to Available-for-sale Securities are excluded from earnings and reported in a separate component of shareholders' equity (other comprehensive income), unless the Available-for-sale security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain (loss) of an Available-for-sale security that is designated as being hedged in a fair value hedge is recognized in earnings during the period of the hedge, as are other than temporary declines in fair value below the cost basis for investments in equity securities and debt securities that an entity intends to sell or it is more likely than not that it will be required to sell before the recovery of its amortized cost basis. Other than temporary declines in fair value below the cost basis for debt securities categorized as Available-for-sale that an entity does not intend to sell and for which it is not more likely than not that the entity will be required to sell before the recovery of its amortized cost basis are bifurcated into credit losses and losses related to all other factors. Other than temporary declines in fair value below cost basis related to credit losses are recognized in earnings, and losses related to all other factors are recognized in other comprehensive income.

+ References

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- Definition

Financial instruments 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 debt and 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.

+ References

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