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								3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013 Equity warrant assets Other assets		Mar. 31, 2012 Equity warrant assets Other assets		Mar. 31, 2013 Fair value accounting Other venture capital investments	Dec. 31, 2012 Fair value accounting Other venture capital investments	Mar. 31, 2013 Non-marketable securities Fair value accounting		Mar. 31, 2012 Non-marketable securities Fair value accounting		Mar. 31, 2013 Non-marketable securities Fair value accounting Venture capital and private equity fund investments	Mar. 31, 2012 Non-marketable securities Fair value accounting Venture capital and private equity fund investments	Mar. 31, 2013 Non-marketable securities Fair value accounting Other venture capital investments	Mar. 31, 2012 Non-marketable securities Fair value accounting Other venture capital investments	Mar. 31, 2012 Non-marketable securities Fair value accounting Other investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 859,141	$ 799,962	$ 66,129	[1]	$ 63,030	[1]	$ 124,786	$ 127,091	$ 793,012	[2]	$ 736,932	[2]	$ 665,921	$ 611,824	$ 127,091	$ 124,121	$ 987
Total Realized and Unrealized Gains (Losses) Included in Income	(26,157)	(12,333)	(1,459)	[1]	(3,795)	[1]			(24,698)	[2]	(8,538)	[2]	(22,510)	(12,104)	(2,188)	3,587	(21)
Purchases	29,910	29,440	0	[1]	0	[1]			29,910	[2]	29,440	[2]	29,744	21,716	166	7,724	0
Sales	(2,271)	(3,950)	(2,250)	[1]	(3,643)	[1]			(21)	[2]	(307)	[2]	0	0	(21)	(307)	0
Issuances	1,926	2,300	1,926	[1]	2,300	[1]			0	[2]	0	[2]	0	0	0	0	0
Distributions and Other Settlements	(17,812)	(25,293)	364	[1]	1	[1]			(18,176)	[2]	(25,294)	[2]	(17,099)	(25,288)	(1,077)	0	(6)
Transfers Into Level 3	0	0	0	[1]	0	[1]			0	[2]	0	[2]	0	0	0	0	0
Transfers Out of Level 3	(5,143)	(266)	(1,582)	[1]	(266)	[1]			(3,561)	[2]	0	[2]	0	0	(3,561)	0	0
Ending Balance	$ 891,908	$ 814,526	$ 66,046	[1]	$ 65,217	[1]	$ 124,786	$ 127,091	$ 825,862	[2]	$ 749,309	[2]	$ 701,076	$ 620,356	$ 124,786	$ 127,951	$ 1,002

[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.