Estimated Fair Values of Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 788,965	$ 570,854
Restricted cash and cash equivalents, Carrying Amount	24,832	21,962
Investments, Carrying Amount	85,699	139,006
Debt, Carrying Amount	92,241	93,735
Forward contracts, Carrying Amount	(9,149)	(5,029)
Cash and cash equivalents, Fair Value	788,965	570,854
Restricted cash and cash equivalents, Fair Value	24,832	21,962
Investments, Fair Value	85,699	139,006
Debt, Fair Value	95,940	96,187
Forward contracts, Fair Value	$ (9,149)	$ (5,029)

For an unclassified balance sheet, this item represents investments in debt and equity securities which are categorized neither as held-to-maturity nor trading.

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