Investment Securities Components of Gains and Losses (Realized and Unrealized) on Investment Securities (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013 company		Dec. 31, 2012		Dec. 31, 2011
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	$ 455,531,000		$ 203,321,000		$ 242,226,000
Gross losses on investment securities	(36,123,000)		(81,207,000)		(47,192,000)
Gains (losses) on investment securities, net	419,408,000		122,114,000		195,034,000
Unrealized valuation gains	219,000,000
Number of portfolio companies	2
Other than temporary impairment losses, investments	3,900,000		0
Cost method accounting | Venture capital and private equity fund investments
Gain (Loss) on Investments [Line Items]
Recognized other-than-temporary impairment (OTTI) losses	1,400,000		1,000,000		1,000,000
Number of impaired investments	43		46		41
Number of investments	288		324		329
Available-for-sale Securities
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	3,887,000	[1]	6,380,000	[1]	37,387,000	[1]
Gross losses on investment securities	(3,349,000)	[1]	(2,139,000)	[1]	(261,000)	[1]
Marketable Securities | Fair value accounting
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	0		8,863,000		912,000
Gross losses on investment securities	0		(1,675,000)		(8,103,000)
Non-marketable securities | Fair value accounting | Venture capital and private equity fund investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	186,404,000		107,507,000		145,892,000
Gross losses on investment securities	(17,185,000)		(63,146,000)		(26,591,000)
Non-marketable securities | Fair value accounting | Other venture capital investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	9,241,000	[2]	58,409,000		36,506,000
Gross losses on investment securities	(3,496,000)		(11,062,000)		(8,918,000)
Non-marketable securities | Fair value accounting | Other investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	0		21,000		40,000
Gross losses on investment securities	0		0		(16,000)
Non-marketable securities | Fair value accounting | Other Securities
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	227,252,000	[2]	0		0
Gross losses on investment securities	(2,962,000)		0		0
Non-marketable securities | Equity method accounting | Other investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	18,235,000		16,923,000		12,445,000
Gross losses on investment securities	(3,111,000)		(1,987,000)		(2,241,000)
Non-marketable securities | Cost method accounting | Venture capital and private equity fund investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	10,081,000		3,503,000		2,517,000
Gross losses on investment securities	(1,700,000)	[3]	(1,079,000)	[3]	(1,028,000)	[3]
Non-marketable securities | Cost method accounting | Other investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	431,000		1,715,000		6,527,000
Gross losses on investment securities	$ (4,320,000)	[4]	$ (119,000)	[4]	$ (34,000)	[4]

[1] 1)Includes realized gains (losses) on sales of available-for-sale securities that are recognized in the income statement. Unrealized gains (losses) on available-for-sale securities are recognized in other comprehensive income. The cost basis of available-for-sale securities sold is determined on a specific identification basis.

[2] Other securities (fair value accounting) and other venture capital investments includes unrealized valuation gains of $219 million for the year ended December 31, 2013 attributable to two of our portfolio companies, FireEye and Twitter. Both FireEye and Twitter are each subject to a lock-up agreement. The extent to which any unrealized gains will become realized is subject to a variety of factors, including, among other things, the expiration of current lock-up agreements to which these securities are subject, the actual sales of securities and the timing of such actual sales.

[3] Includes OTTI of $1.4 million from the declines in value for 43 of the 288 investments, $1.0 million from the declines in value for 46 of the 324 investments, and 1.0 million from the declines in value for 41 of the 329 investments held at December 31, 2013, 2012, and 2011, respectively. We concluded that any declines in value for the remaining investments were temporary, and as such, no OTTI was required to be recognized.

[4] Includes OTTI of $3.9 million impairment charge on a single direct equity investment. We concluded that any declines in value for the remaining investments were temporary, and as such, no OTTI was required to be recognized. There were no recognized OTTI amounts for the years ended December 31, 2012 and 2011.