Fair Value of Financial Instruments - Additional Information about Level 3 Assets Measured at Fair Value on a Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended		3 Months Ended								9 Months Ended				3 Months Ended				9 Months Ended			3 Months Ended		9 Months Ended				3 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Equity warrant assets Other assets		Sep. 30, 2013 Equity warrant assets Other assets		Sep. 30, 2014 Non-marketable securities Fair value accounting		Sep. 30, 2013 Non-marketable securities Fair value accounting		Sep. 30, 2014 Non-marketable securities Fair value accounting		Sep. 30, 2013 Non-marketable securities Fair value accounting		Sep. 30, 2014 Non-marketable securities Fair value accounting Venture capital and private equity fund investments	Sep. 30, 2013 Non-marketable securities Fair value accounting Venture capital and private equity fund investments	Sep. 30, 2014 Non-marketable securities Fair value accounting Other venture capital investments	Sep. 30, 2013 Non-marketable securities Fair value accounting Other venture capital investments	Sep. 30, 2013 Non-marketable securities Fair value accounting Other venture capital investments		Sep. 30, 2014 Non-marketable securities Fair value accounting Other securities	Sep. 30, 2013 Non-marketable securities Fair value accounting Other investments	Dec. 31, 2013 Non-marketable securities Fair value accounting Other investments	Sep. 30, 2014 Fair Value, Measurements, Recurring Equity warrant assets Other assets		Sep. 30, 2013 Fair Value, Measurements, Recurring Equity warrant assets Other assets		Sep. 30, 2014 Fair Value, Measurements, Recurring Fair value accounting Other securities	Sep. 30, 2014 Fair Value, Measurements, Recurring Fair value accounting Other securities	Sep. 30, 2014 Fair Value, Measurements, Recurring Non-marketable securities Fair value accounting Venture capital and private equity fund investments	Sep. 30, 2013 Fair Value, Measurements, Recurring Non-marketable securities Fair value accounting Venture capital and private equity fund investments	Sep. 30, 2014 Fair Value, Measurements, Recurring Non-marketable securities Fair value accounting Other venture capital investments	Sep. 30, 2013 Fair Value, Measurements, Recurring Non-marketable securities Fair value accounting Other venture capital investments	Sep. 30, 2013 Fair Value, Measurements, Recurring Non-marketable securities Fair value accounting Other investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 1,177,228	$ 938,244	$ 1,314,951	$ 859,141	$ 87,151	[1]	$ 73,229	[1]	$ 1,090,077	[2]	$ 865,015	[2]	$ 1,215,060	[2]	$ 793,012	[2]	$ 1,040,522	$ 741,522	$ 43,747	$ 123,493				$ 0	$ 217,054	$ 99,891	[1]	$ 66,129	[1]	$ 5,808	$ 319,249	$ 862,972	$ 665,921	$ 32,839	$ 127,091	$ 0
Total Realized and Unrealized Gains (Losses) Included in Income	62,811	200,334	355,935	265,748	13,805	[1]	18,215	[1]	49,006	[2]	182,119	[2]	304,610	[2]	239,606	[2]	43,460	34,288	5,546	4,530				143,301		51,325	[1]	26,142	[1]	0	104,310	192,240	90,526	8,060	5,779	143,301
Purchases	55,341	42,720	182,248	108,232	0	[1]	0	[1]	55,341	[2]	42,720	[2]	182,248	[2]	108,232	[2]	49,037	41,704	6,304	1,016				0		0	[1]	0	[1]	0	0	159,448	107,022	22,800	1,210	0
Sales	(21,686)	(6,362)	(129,602)	(11,186)	(10,564)	[1]	(6,366)	[1]	(11,122)	[2]	4	[2]	(62,401)	[2]	(381)	[2]	0	0	(11,122)	4				0		(67,201)	[1]	(10,805)	[1]	0	(46,840)	0	0	(15,561)	(381)	0
Issuances	2,932	2,995	9,098	7,309	2,932	[1]	2,995	[1]	0	[2]	0	[2]	0	[2]	0	[2]	0	0	0	0				0		9,098	[1]	7,309	[1]	0	0	0	0	0	0	0
Distributions and Other Settlements	(54,210)	(43,581)	(134,763)	(89,253)	510	[1]	365	[1]	(54,720)	[2]	(43,946)	[2]	(136,481)	[2]	(90,996)	[2]	(54,108)	(44,015)	(612)	(73,684)				73,753		1,718	[1]	1,743	[1]	0	3,417	(135,749)	(89,970)	(4,149)	(74,779)	73,753
Transfers Out of Level 3	(6,245)	(312)	(381,696)	(5,953)	(437)	[1]	(312)	[1]	(5,808)	[2]	0	[2]	(380,262)	[2]			0	0	0	0	(3,561)	[2]	(380,136)	0		(1,434)	[1]	(2,392)	[1]			0	0	(126)	(3,561)	0
Ending Balance	$ 1,216,171	$ 1,134,038	$ 1,216,171	$ 1,134,038	$ 93,397	[1]	$ 88,126	[1]	$ 1,122,774	[2]	$ 1,045,912	[2]	$ 1,122,774	[2]	$ 1,045,912	[2]	$ 1,078,911	$ 773,499	$ 43,863	$ 55,359	$ 55,359			$ 217,054	$ 217,054					$ 0	$ 0

[1] Realized and unrealized gains (losses) are recorded in the line item “gains on derivative instruments, net”, a component of noninterest income.

[2] Realized and unrealized gains (losses) are recorded in the line items “gains on investment securities, net”, and “other noninterest income”, components of noninterest income.