Components of Gains and Losses (Realized and Unrealized) on Investment Securities (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	$ 203,321		$ 242,226		$ 138,770
Gross losses on investment securities	(81,207)		(47,192)		(45,410)
Gains (losses) on investment securities, net	122,114		195,034		93,360
Gains (losses) attributable to noncontrolling interests, including carried interest	85,640		125,042		52,586
Available-for-sale Securities
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	6,380	[1]	37,387	[1]	27,110	[1]
Gross losses on investment securities	2,139	[1]	261	[1]	2,287	[1]
Marketable Securities | Fair value accounting
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	8,863		912		8,160
Gross losses on investment securities	1,675		8,103		9,855
Non-marketable securities | Fair value accounting | Venture capital and private equity fund investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	107,507		145,892		63,137
Gross losses on investment securities	63,146		26,591		19,497
Non-marketable securities | Fair value accounting | Other venture capital investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	58,409		36,506		29,455
Gross losses on investment securities	11,062		8,918		11,079
Non-marketable securities | Fair value accounting | Other investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	21		40		140
Gross losses on investment securities	0		16		158
Non-marketable securities | Equity method accounting | Other investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	16,923		12,445		8,551
Gross losses on investment securities	1,987		2,241		616
Non-marketable securities | Cost method accounting | Venture capital and private equity fund investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	3,503		2,517		1,739
Gross losses on investment securities	1,079		1,028		1,793
Non-marketable securities | Cost method accounting | Other investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	1,715		6,527		478
Gross losses on investment securities	$ 119		$ 34		$ 125

[1] The cost basis of available-for-sale securities sold is determined on a specific identification basis.