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		3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Equity warrant assets Other assets		Sep. 30, 2012 Equity warrant assets Other assets		Sep. 30, 2013 Equity warrant assets Other assets		Sep. 30, 2012 Equity warrant assets Other assets		Sep. 30, 2013 Fair value accounting Other venture capital investments	Dec. 31, 2012 Fair value accounting Other venture capital investments	Sep. 30, 2013 Non-marketable securities Fair value accounting		Sep. 30, 2012 Non-marketable securities Fair value accounting		Sep. 30, 2013 Non-marketable securities Fair value accounting		Sep. 30, 2012 Non-marketable securities Fair value accounting		Sep. 30, 2013 Non-marketable securities Fair value accounting Venture capital and private equity fund investments	Sep. 30, 2012 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, 2012 Non-marketable securities Fair value accounting Venture capital and private equity fund investments	Sep. 30, 2013 Non-marketable securities Fair value accounting Other venture capital investments	Sep. 30, 2012 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, 2012 Non-marketable securities Fair value accounting Other venture capital investments	Sep. 30, 2012 Non-marketable securities Fair value accounting Other investments	Sep. 30, 2012 Non-marketable securities Fair value accounting Other investments	Sep. 30, 2013 Fair Value, Measurements, Recurring Fair value accounting Other Securities [Member]	Sep. 30, 2013 Fair Value, Measurements, Recurring Fair value accounting Other Securities [Member]	Sep. 30, 2013 Fair Value, Measurements, Recurring Level 3 Fair value accounting Other Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 938,244	$ 828,326	$ 859,141	$ 799,962	$ 73,229	[1]	$ 68,619	[1]	$ 66,129		$ 63,030		$ 55,359	$ 127,091	$ 865,015	[2]	$ 759,707	[2]	$ 793,012	[2]	$ 736,932	[2]	$ 741,522	$ 639,596	$ 665,921	$ 611,824	$ 123,493	$ 120,111	$ 127,091	$ 124,121	$ 0	$ 987	$ 0	$ 0	$ 217,054
Total Realized and Unrealized Gains (Losses) Included in Income	(200,334)	(14,563)	(265,748)	(43,766)	(18,215)	[1]	800	[1]	(26,142)		(8,848)				(182,119)	[2]	(15,363)	[2]	(239,606)	[2]	(34,918)	[2]	(34,288)	(12,104)	(90,526)	(38,765)	(4,530)	(3,259)	(5,779)	3,868	0	(21)	(143,301)	(143,301)
Purchases	42,720	36,045	108,232	99,061	0	[1]	0	[1]	0		0				42,720	[2]	36,045	[2]	108,232	[2]	99,061	[2]	41,704	35,092	107,022	90,173	1,016	953	1,210	8,888	0	0	0	0
Sales	(6,362)	(11,156)	(11,186)	(25,113)	(6,366)	[1]	(5,954)	[1]	(10,805)		(15,672)				4	[2]	(5,202)	[2]	(381)	[2]	(9,441)	[2]	0	0	0	0	4	(5,202)	(381)	(9,441)	0	0	0	0
Issuances	2,995	2,994	7,309	9,167	2,995	[1]	2,994	[1]	7,309		9,167				0	[2]	0	[2]	0	[2]	0	[2]	0	0	0	0	0	0	0	0	0	0	0	0
Distributions and Other Settlements	(43,581)	(27,904)	(89,253)	(82,865)	365	[1]	0	[1]	1,743		1				(43,946)	[2]	(27,904)	[2]	(90,996)	[2]	(82,866)	[2]	(44,015)	(28,383)	(89,970)	(82,353)	(73,684)	479	(74,779)	495	0	(1,008)	73,753	73,753
Transfers Into Level 3	0	0	0	0	0	[1]	0	[1]	0		0				0	[2]	0	[2]	0	[2]	0	[2]	0	0	0	0	0	0	0	0	0	0	0	0
Transfers Out of Level 3	(312)	(1,146)	(5,953)	(2,256)	(312)	[1]	(168)	[1]	(2,392)		(683)				0	[2]	(978)	[2]	(3,561)	[2]	(1,573)	[2]	0	0	0	0	0	(978)	(3,561)	(1,573)	0	0	0	0
Ending Balance	$ 1,134,038	$ 841,722	$ 1,134,038	$ 841,722	$ 88,126	[1]	$ 64,691	[1]	$ 88,126	[1]	$ 64,691	[1]	$ 55,359	$ 127,091	$ 1,045,912	[2]	$ 777,031	[2]	$ 1,045,912	[2]	$ 777,031	[2]	$ 773,499	$ 658,409	$ 773,499	$ 658,409	$ 55,359	$ 118,622	$ 55,359	$ 118,622	$ 0	$ 0	$ 217,054	$ 217,054	$ 217,054

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

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