Investment Securities - Components of Gains and Losses (Realized and Unrealized) on Investment Securities (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014 Investment	Jun. 30, 2013 Investment	Jun. 30, 2014 Investment	Jun. 30, 2013 Investment	Dec. 31, 2013 Investment
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	$ 113,685,000	$ 55,528,000	$ 351,905,000	$ 91,350,000
Gross losses on investment securities	(171,005,000)	(14,967,000)	(185,313,000)	(23,351,000)
(Losses) gains on investment securities, net	(57,320,000)	40,561,000	166,592,000	67,999,000
Fair value accounting | Other securities
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	13,816,000	2,427,000
Gross losses on investment securities	(101,014,000)	(461,000)
Net gains (losses) on securities	(84,900,000)		(28,100,000)
Realized gains	20,400,000		66,500,000
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	300,000	400,000	800,000
Number of other-than-temporary impaired investments	12	12	18	27
Number of investments	282	303	282	303	288
Available-for-sale Securities
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	224,000	2,850,000	597,000	2,850,000
Gross losses on investment securities	(16,704,000)	(2,075,000)	(17,017,000)	(2,120,000)
Non-marketable securities | Fair value accounting | Venture capital and private equity fund investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	88,003,000	44,339,000	199,439,000	71,720,000
Gross losses on investment securities	(50,558,000)	(10,703,000)	(50,659,000)	(15,445,000)
Non-marketable securities | Fair value accounting | Other venture capital investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	1,973,000	200,000	4,555,000	2,840,000
Gross losses on investment securities	(1,297,000)	(1,190,000)	(2,041,000)	(1,654,000)
Non-marketable securities | Fair value accounting | Other securities
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities			130,566,000	4,345,000
Gross losses on investment securities			(113,787,000)	(2,534,000)
Non-marketable securities | Equity method accounting | Other investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	2,886,000	4,754,000	6,528,000	7,469,000
Gross losses on investment securities	(828,000)	(232,000)	(1,040,000)	(477,000)
Non-marketable securities | Cost method accounting | Venture capital and private equity fund investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	1,762,000	767,000	5,065,000	1,790,000
Gross losses on investment securities	(353,000)	(304,000)	(509,000)	(773,000)
Non-marketable securities | Cost method accounting | Other investments
Gain (Loss) on Investments [Line Items]
Gross gains on investment securities	5,021,000	191,000	5,155,000	336,000
Gross losses on investment securities	$ (251,000)	$ (2,000)	$ (260,000)	$ (348,000)