Estimated Fair Values of Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 638,794	$ 570,854
Restricted cash and cash equivalents, carrying amount	23,074	21,962
Investments, carrying amount	58,834	139,006
Debt, carrying amount	108,286	93,735
Forward contracts, carrying amount	7,274	(5,029)
Cash and cash equivalents, fair value	638,794	570,854
Restricted cash and cash equivalents, fair value	23,074	21,962
Investments, fair value	58,834	139,006
Debt, fair value	111,901	96,187
Forward contracts, fair value	$ 7,274	$ (5,029)

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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