Components of Gains and Losses (Realized and Unrealized) on Investment Securities (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	$ 49,660		$ 82,779		$ 79,776		$ 137,563
Gross losses on investment securities	(23,851)		(11,099)		(46,128)		(14,546)
Gains (losses) on investment securities, net	25,809		71,680		33,648		123,017
Gains (losses) attributable to noncontrolling interests, including carried interest	14,502		26,437		21,840		69,822
Cost method accounting | Other investments
Gain (Loss) on Investments [Line Items]
Gross losses on investment securities	(1)		(31)		(66)		(31)
Available-for-sale Securities
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	5,322	[1]	37,314	[1]	5,343	[1]	37,377	[1]
Gross losses on investment securities	(755)	[1]	(93)	[1]	(1,650)	[1]	(94)	[1]
Marketable Securities | Fair value accounting
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	3,303				3,619		442
Gross losses on investment securities	(754)		(3,307)		(754)		(4,115)
Non-marketable securities | Fair value accounting | Venture capital and private equity fund investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	33,288		37,205		59,398		82,704
Gross losses on investment securities	(18,618)		(4,845)		(32,533)		(6,901)
Non-marketable securities | Fair value accounting | Other venture capital investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	1,556		2,071		3,333		7,019
Gross losses on investment securities	(3,219)		(1,420)		(9,882)		(1,664)
Non-marketable securities | Fair value accounting | Other investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities					21		20
Non-marketable securities | Equity method accounting | Other investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	5,389		3,132		6,811		6,516
Gross losses on investment securities	(327)		(1,110)		(703)		(1,309)
Non-marketable securities | Cost method accounting | Venture capital and private equity fund investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	538		801		945		1,056
Gross losses on investment securities	(177)		(293)		(540)		(432)
Non-marketable securities | Cost method accounting | Other investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	$ 264		$ 2,256		$ 306		$ 2,429

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