Additional Information about Level 3 Assets Measured at Fair Value on a Recurring Basis (Detail) (USD $)	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 828,326,000		$ 679,960,000		$ 799,962,000		$ 547,608,000
Total Realized and Unrealized Gains (Losses) Included in Income	(14,563,000)		(57,454,000)		(43,766,000)		(152,047,000)
Purchases	36,045,000		44,783,000		99,061,000		132,929,000
Sales	11,156,000		15,762,000		25,113,000		47,402,000
Issuances	2,994,000		2,876,000		9,167,000		10,058,000
Distributions and Other Settlements	27,904,000		15,634,000		82,865,000		40,935,000
Transfers Into Level 3	0		0		0		0
Transfers Out of Level 3	1,146,000		0		2,256,000		628,000
Ending Balance	841,722,000		753,677,000		841,722,000		753,677,000
Equity Warrant Asset | Other assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	68,619,000		49,777,000		63,030,000		43,537,000
Total Realized and Unrealized Gains (Losses) Included in Income	800,000		(8,192,000)		(8,848,000)		(21,403,000)
Purchases	0		0		0		0
Sales	5,954,000		6,427,000		15,672,000		19,889,000
Issuances	2,994,000		2,876,000		9,167,000		10,058,000
Distributions and Other Settlements	0		0		(1,000)		63,000
Transfers Into Level 3	0		0		0		0
Transfers Out of Level 3	168,000		0		683,000		628,000
Ending Balance	64,691,000	[1]	54,418,000	[1]	64,691,000	[1]	54,418,000	[1]
Fair value accounting | Other venture capital investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Ending Balance	118,622,000				118,622,000
Non-marketable securities | Fair value accounting
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	759,707,000	[2]	630,183,000	[2]	736,932,000	[2]	504,071,000	[2]
Total Realized and Unrealized Gains (Losses) Included in Income	(15,363,000)	[2]	(49,262,000)	[2]	(34,918,000)	[2]	(130,644,000)	[2]
Purchases	36,045,000	[2]	44,783,000	[2]	99,061,000	[2]	132,929,000	[2]
Sales	5,202,000	[2]	9,335,000	[2]	9,441,000	[2]	27,513,000	[2]
Issuances	0		0		0		0
Distributions and Other Settlements	27,904,000	[2]	15,634,000	[2]	82,866,000	[2]	40,872,000	[2]
Transfers Into Level 3	0		0		0		0
Transfers Out of Level 3	978,000	[2]	0	[2]	1,573,000	[2]	0	[2]
Ending Balance	777,031,000	[2]	699,259,000	[2]	777,031,000	[2]	699,259,000	[2]
Non-marketable securities | Fair value accounting | Venture capital and private equity fund investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	639,596,000		515,118,000		611,824,000		391,247,000
Total Realized and Unrealized Gains (Losses) Included in Income	(12,104,000)		(32,041,000)		(38,765,000)		(108,032,000)
Purchases	35,092,000		42,590,000		90,173,000		119,990,000
Sales	0		0		0		0
Issuances	0		0		0		0
Distributions and Other Settlements	28,383,000		11,623,000		82,353,000		41,143,000
Transfers Into Level 3	0		0		0		0
Transfers Out of Level 3	0		0		0		0
Ending Balance	658,409,000		578,126,000		658,409,000		578,126,000
Non-marketable securities | Fair value accounting | Other venture capital investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	120,111,000		114,070,000		124,121,000		111,843,000
Total Realized and Unrealized Gains (Losses) Included in Income	(3,259,000)		(17,237,000)		3,868,000		(22,608,000)
Purchases	953,000		2,193,000		8,888,000		12,939,000
Sales	5,202,000		9,335,000		9,441,000		27,513,000
Issuances	0		0		0		0
Distributions and Other Settlements	(479,000)		4,005,000		(495,000)		(283,000)
Transfers Into Level 3	0		0		0		0
Transfers Out of Level 3	978,000		0		1,573,000		0
Ending Balance	118,622,000		120,160,000		118,622,000		120,160,000
Non-marketable securities | Fair value accounting | Other investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance			995,000		987,000		981,000
Total Realized and Unrealized Gains (Losses) Included in Income			16,000		(21,000)		(4,000)
Purchases			0		0		0
Sales			0		0		0
Issuances			0		0		0
Distributions and Other Settlements			6,000		1,008,000		12,000
Transfers Into Level 3			0		0		0
Transfers Out of Level 3			0		0		0
Ending Balance	$ 0		$ 973,000		$ 0		$ 973,000

[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.