Investment Securities - Components of Gains and Losses (Realized and Unrealized) on Investment Securities (Detail) (USD $)	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013	Jun. 30, 2012
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	$ 55,528,000		$ 49,660,000		$ 91,350,000	$ 79,776,000
Gross losses on investment securities	(14,967,000)		(23,851,000)		(23,351,000)	(46,128,000)
Gains on investment securities, net	40,561,000		25,809,000		67,999,000	33,648,000
Gains attributable to noncontrolling interests, including carried interest	31,067,000		14,502,000		53,363,000	21,840,000
Cost method accounting | Venture capital and private equity fund investments
Gain (Loss) on Investments [Line Items]
Recognized other-than-temporary impairment (OTTI) losses	300,000				800,000
Number of other-than-temporary impaired investments	12				27
Available-for-sale Securities
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	2,850,000	[1]	5,322,000	[1]	2,850,000	5,343,000
Gross losses on investment securities	(2,075,000)	[1]	(755,000)	[1]	2,120,000	1,650,000
Marketable Securities | Fair value accounting
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	2,427,000		3,303,000		4,345,000	3,619,000
Gross losses on investment securities	(461,000)		(754,000)		2,534,000	754,000
Non-marketable securities | Fair value accounting | Venture capital and private equity fund investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	44,339,000		33,288,000		71,720,000	59,398,000
Gross losses on investment securities	(10,703,000)		(18,618,000)		15,445,000	32,533,000
Non-marketable securities | Fair value accounting | Other venture capital investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	200,000		1,556,000		2,840,000	3,333,000
Gross losses on investment securities	(1,190,000)		(3,219,000)		1,654,000	9,882,000
Non-marketable securities | Fair value accounting | Other investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	0		0		0	21,000
Non-marketable securities | Equity method accounting | Other investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	4,754,000		5,389,000		7,469,000	6,811,000
Gross losses on investment securities	(232,000)		(327,000)		477,000	703,000
Non-marketable securities | Cost method accounting | Venture capital and private equity fund investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	767,000		538,000		1,790,000	945,000
Gross losses on investment securities	(304,000)		(177,000)		773,000	540,000
Non-marketable securities | Cost method accounting | Other investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	191,000		264,000		336,000	306,000
Gross losses on investment securities	$ (2,000)		$ (1,000)		$ 348,000	$ 66,000

[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 and not shown in the table above. The cost basis of available-for-sale securities sold is determined on a specific identification basis.