Marketable Securities and Time Deposits - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Schedule Of Marketable Securities [Line Items]
Unrealized loss outstanding on securities, less than twelve months	$ 23,155
Proceeds from maturity of available-for-sale marketable securities	6,056	5,930
Proceeds from sales of available-for-sale marketable securities	7,937	5,068
Net realized gains from the sale of available-for sale securities	163	71
Marketable securities
Schedule Of Marketable Securities [Line Items]
Marketable securities with outstanding unrealized gain (loss)	$ 23,155

This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for less than twelve months.

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The aggregate net change in the difference between the fair value and the carrying value, or in the comparative fair values, of marketable securities categorized as trading held at each balance sheet date, that was included in earnings for the period, which may have arisen from (a) securities classified as trading, (b) the unrealized holding gain (loss) on held-to-maturity securities transferred to the trading security category, and (c) the cumulative unrealized gain (loss) which was included in other comprehensive income (a separate component of shareholders' equity) on available-for-sale securities transferred to trading securities during the period.

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