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		6 Months Ended		3 Months Ended				6 Months Ended						3 Months Ended				6 Months Ended				3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Equity warrant assets Other assets		Jun. 30, 2012 Equity warrant assets Other assets		Jun. 30, 2013 Equity warrant assets Other assets		Jun. 30, 2012 Equity warrant assets Other assets		Jun. 30, 2013 Fair value accounting Other venture capital investments	Dec. 31, 2012 Fair value accounting Other venture capital investments	Jun. 30, 2013 Non-marketable securities Fair value accounting		Jun. 30, 2012 Non-marketable securities Fair value accounting		Jun. 30, 2013 Non-marketable securities Fair value accounting		Jun. 30, 2012 Non-marketable securities Fair value accounting		Jun. 30, 2013 Non-marketable securities Fair value accounting Venture capital and private equity fund investments	Jun. 30, 2012 Non-marketable securities Fair value accounting Venture capital and private equity fund investments	Jun. 30, 2013 Non-marketable securities Fair value accounting Venture capital and private equity fund investments	Jun. 30, 2012 Non-marketable securities Fair value accounting Venture capital and private equity fund investments	Jun. 30, 2013 Non-marketable securities Fair value accounting Other venture capital investments	Jun. 30, 2012 Non-marketable securities Fair value accounting Other venture capital investments	Jun. 30, 2013 Non-marketable securities Fair value accounting Other venture capital investments	Jun. 30, 2012 Non-marketable securities Fair value accounting Other venture capital investments	Jun. 30, 2013 Non-marketable securities Fair value accounting Other investments	Jun. 30, 2012 Non-marketable securities Fair value accounting Other investments	Jun. 30, 2013 Non-marketable securities Fair value accounting Other investments	Jun. 30, 2012 Non-marketable securities Fair value accounting Other investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unrealized gains included in earnings attributable to Level 3 assets still held	$ 39,421	$ 28,250	$ 64,407	$ 37,813	$ 5,240		$ 2,888		$ 6,279		$ 3,392				$ 34,181		$ 25,362		$ 58,128		$ 34,421		$ 34,390	$ 14,543	$ 57,011	$ 26,192	$ (209)	$ 10,819	$ 1,117	$ 8,208	$ 0		$ 0	$ 21
Beginning Balance	891,908	814,526	859,141	799,962	66,046	[1]	65,217	[1]	66,129		63,030		123,493	127,091	825,862	[2]	749,309	[2]	793,012	[2]	736,932	[2]	701,076	620,356	665,921	611,824	124,786	127,951	127,091	124,121		1,002		987
Total Realized and Unrealized Gains (Losses) Included in Income	(39,257)	(16,870)	(65,414)	(29,203)	(6,468)	[1]	(5,853)	[1]	(7,927)		(9,648)				(32,789)	[2]	(11,017)	[2]	(57,487)	[2]	(19,555)	[2]	(33,728)	(14,557)	(56,238)	(26,661)	939	3,540	(1,249)	7,127		0		(21)
Purchases	35,602	33,576	65,512	63,016	0	[1]	0	[1]	0		0				35,602	[2]	33,576	[2]	65,512	[2]	63,016	[2]	35,574	33,365	65,318	55,081	28	211	194	7,935		0		0
Sales	(2,553)	(10,007)	(4,824)	(13,957)	(2,189)	[1]	(6,075)	[1]	(4,439)		(9,718)				(364)	[2]	(3,932)	[2]	(385)	[2]	(4,239)	[2]	0	0	0	0	(364)	(3,932)	(385)	(4,239)		0		0
Issuances	2,388	3,873	4,314	6,173	2,388	[1]	3,873	[1]	4,314		6,173				0	[2]	0	[2]	0	[2]	0	[2]	0	0	0	0	0	0	0	0		0		0
Distributions and Other Settlements	(27,860)	(29,668)	(45,672)	(54,961)	1,014	[1]	0	[1]	1,378		1				(28,874)	[2]	(29,668)	[2]	(47,050)	[2]	(54,962)	[2]	(28,856)	(28,682)	(45,955)	(53,970)	(18)	16	(1,095)	16		(1,002)		(1,008)
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
Transfers Out of Level 3	(498)	(844)	(5,641)	(1,110)	(498)	[1]	(249)	[1]	(2,080)		(515)				0	[2]	(595)	[2]	(3,561)	[2]	(595)	[2]	0	0	0	0	0	(595)	(3,561)	(595)		0		0
Ending Balance	938,244	828,326	938,244	828,326	73,229	[1]	68,619	[1]	73,229	[1]	68,619	[1]	123,493	127,091	865,015	[2]	759,707	[2]	865,015	[2]	759,707	[2]	741,522	639,596	741,522	639,596	123,493	120,111	123,493	120,111		0		0
Unrealized gains attributable to noncontrolling interests	$ 28,482	$ 21,721	$ 50,245	$ 28,969

[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.