Investments in Available for Sale Securities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Gross Amortized Costs	$ 2,918,761	$ 4,169,176
Gross Unrealized Gains	2,743	2,582
Gross Unrealized Losses	(1,317)	(700)
Estimated Fair Value, Total investments in available-for-sale securities	2,920,187	4,171,058
Government and agency securities
Schedule of Available-for-sale Securities [Line Items]
Gross Amortized Costs	538,397	1,312,876
Gross Unrealized Gains	65	985
Gross Unrealized Losses	(101)	(45)
Estimated Fair Value, Total investments in available-for-sale securities	538,361	1,313,816
Corporate Debt Securities, Commercial Paper, And Bank Certificates Of Deposit
Schedule of Available-for-sale Securities [Line Items]
Gross Amortized Costs	2,380,134	2,039,809
Gross Unrealized Gains	2,525	1,597
Gross Unrealized Losses	(1,216)	(622)
Estimated Fair Value, Total investments in available-for-sale securities	2,381,443	2,040,784
Corporate Equity And Other Marketable Securities
Schedule of Available-for-sale Securities [Line Items]
Gross Amortized Costs	230	230
Gross Unrealized Gains	153
Gross Unrealized Losses		(33)
Estimated Fair Value, Total investments in available-for-sale securities	383	197
Redeemable Preferred Stock | Alibaba Group
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