Fair Value Hierarchy For Financial Assets And Liabilities Measured At Fair Value (Detail) (USD $)	Dec. 31, 2011	Dec. 31, 2010
Schedule of Investments [Line Items]
Total cash and investments	$ 10,843,129,000	$ 9,546,055,000
Foreign exchange derivative assets	23,372,000	19,655,000
Foreign exchange derivative liabilities	(27,741,000)	(21,975,000)
Cash
Schedule of Investments [Line Items]
Total cash and investments	3,096,275,000	1,534,786,000
Cash Equivalents
Schedule of Investments [Line Items]
Total cash and investments	1,434,761,000	2,584,352,000
US Government Agencies Debt Securities
Schedule of Investments [Line Items]
Total cash and investments	2,484,961,000	1,746,394,000
US Corporate Debt Securities
Schedule of Investments [Line Items]
Total cash and investments	1,407,753,000	1,251,626,000
High Yield Corporate Debt Securities
Schedule of Investments [Line Items]
Total cash and investments	447,479,000	437,832,000
Asset-backed Securities
Schedule of Investments [Line Items]
Total cash and investments	29,148,000	34,881,000
Municipal Obligations
Schedule of Investments [Line Items]
Total cash and investments	816,081,000	1,095,901,000
Auction Rate Securities
Schedule of Investments [Line Items]
Total cash and investments	74,596,000	146,044,000
Foreign Debt Securities
Schedule of Investments [Line Items]
Total cash and investments	987,074,000	659,415,000
Publicly Traded Equity Securities
Schedule of Investments [Line Items]
Total cash and investments	65,001,000	54,824,000
Commodity Derivative Liabilities
Schedule of Investments [Line Items]
Derivative liabilities	(3,093,000)	(647,000)
Interest Rate Swap
Schedule of Investments [Line Items]
Derivative liabilities	(19,872,000)	(7,762,000)
Fair Value, Inputs, Level 1
Schedule of Investments [Line Items]
Total cash and investments	5,765,317,000	5,104,947,000
Fair Value, Inputs, Level 1 | Cash
Schedule of Investments [Line Items]
Total cash and investments	3,096,275,000	1,534,786,000
Fair Value, Inputs, Level 1 | Cash Equivalents
Schedule of Investments [Line Items]
Total cash and investments	1,424,761,000	2,522,172,000
Fair Value, Inputs, Level 1 | US Government Agencies Debt Securities
Schedule of Investments [Line Items]
Total cash and investments	1,179,280,000	993,165,000
Fair Value, Inputs, Level 1 | Publicly Traded Equity Securities
Schedule of Investments [Line Items]
Total cash and investments	65,001,000	54,824,000
Fair Value, Inputs, Level 2
Schedule of Investments [Line Items]
Total cash and investments	5,003,216,000	4,295,064,000
Foreign exchange derivative assets	23,372,000	19,655,000
Foreign exchange derivative liabilities	(27,741,000)	(21,975,000)
Fair Value, Inputs, Level 2 | Cash Equivalents
Schedule of Investments [Line Items]
Total cash and investments	10,000,000	62,180,000
Fair Value, Inputs, Level 2 | US Government Agencies Debt Securities
Schedule of Investments [Line Items]
Total cash and investments	1,305,681,000	753,229,000
Fair Value, Inputs, Level 2 | US Corporate Debt Securities
Schedule of Investments [Line Items]
Total cash and investments	1,407,753,000	1,251,626,000
Fair Value, Inputs, Level 2 | High Yield Corporate Debt Securities
Schedule of Investments [Line Items]
Total cash and investments	447,479,000	437,832,000
Fair Value, Inputs, Level 2 | Asset-backed Securities
Schedule of Investments [Line Items]
Total cash and investments	29,148,000	34,881,000
Fair Value, Inputs, Level 2 | Municipal Obligations
Schedule of Investments [Line Items]
Total cash and investments	816,081,000	1,095,901,000
Fair Value, Inputs, Level 2 | Foreign Debt Securities
Schedule of Investments [Line Items]
Total cash and investments	987,074,000	659,415,000
Fair Value, Inputs, Level 2 | Commodity Derivative Liabilities
Schedule of Investments [Line Items]
Derivative liabilities	(3,093,000)	(647,000)
Fair Value, Inputs, Level 2 | Interest Rate Swap
Schedule of Investments [Line Items]
Derivative liabilities	(19,872,000)	(7,762,000)
Fair Value, Inputs, Level 3
Schedule of Investments [Line Items]
Total cash and investments	74,596,000	146,044,000
Fair Value, Inputs, Level 3 | Auction Rate Securities
Schedule of Investments [Line Items]
Total cash and investments	$ 74,596,000	$ 146,044,000