Investments in Available for Sale Securities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Gross Amortized Costs	$ 4,169,176	$ 968,607
Gross Unrealized Gains	2,582	2,079
Gross Unrealized Losses	(700)	(2,376)
Estimated Fair Value, Total investments in available-for-sale securities	4,171,058	968,310
Government and agency securities
Schedule of Available-for-sale Securities [Line Items]
Gross Amortized Costs	1,312,876	599,582
Gross Unrealized Gains	985	1,054
Gross Unrealized Losses	(45)	(172)
Estimated Fair Value, Total investments in available-for-sale securities	1,313,816	600,464
Corporate Debt Securities, Commercial Paper, And Bank Certificates Of Deposit
Schedule of Available-for-sale Securities [Line Items]
Gross Amortized Costs	2,039,809	366,264
Gross Unrealized Gains	1,597	1,025
Gross Unrealized Losses	(622)	(226)
Estimated Fair Value, Total investments in available-for-sale securities	2,040,784	367,063
Corporate Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Gross Amortized Costs	230	2,761
Gross Unrealized Losses	(33)	(1,978)
Estimated Fair Value, Total investments in available-for-sale securities	197	783
Alibaba Group \| Preferred Stock
Schedule of Available-for-sale Securities [Line Items]
Gross Amortized Costs	816,261
Estimated Fair Value, Total investments in available-for-sale securities	$ 816,261

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

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Reference 8: http://www.xbrl.org/2003/role/presentationRef

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Reference 9: http://www.xbrl.org/2003/role/presentationRef

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Reference 10: http://www.xbrl.org/2003/role/presentationRef

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+ Details

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References+ Details

- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

+ References+ Details