Investment Securities - Components of Gains and Losses (Realized and Unrealized) on Investment Securities (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	$ 35,822		$ 30,116
Gross losses on investment securities	(8,384)		(22,277)
Gains on investment securities, net	27,438		7,839
Gains attributable to noncontrolling interests, including carried interest	22,296		7,338
Available-for-sale Securities
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	0	[1]	21	[1]
Gross losses on investment securities	(45)	[1]	(895)	[1]
Marketable Securities | Fair value accounting
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	1,918		316
Gross losses on investment securities	(2,073)		0
Non-marketable securities | Fair value accounting | Venture capital and private equity fund investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	27,381		26,110
Gross losses on investment securities	(4,742)		(13,915)
Non-marketable securities | Fair value accounting | Other venture capital investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	2,640		1,777
Gross losses on investment securities	(464)		(6,663)
Non-marketable securities | Fair value accounting | Other investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	0		21
Non-marketable securities | Equity method accounting | Other investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	2,715		1,422
Gross losses on investment securities	(245)		(376)
Non-marketable securities | Cost method accounting | Venture capital and private equity fund investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	1,023		407
Gross losses on investment securities	(469)		(363)
Non-marketable securities | Cost method accounting | Other investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	145		42
Gross losses on investment securities	$ (346)		$ (65)

[1] Includes realized gains on sales of available-for-sale securities that are recognized in the income statement. Unrealized gains 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.