Unrealized Gains (Losses) Included in Earnings Attributable to Level 3 Assets Held (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2011		Sep. 30, 2011
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Unrealized Gains (Losses) [Line Items]
Unrealized (losses) gains included in earnings attributable to Level 3 assets still held	$ 39,887		$ 100,953
Investment company fair value accounting | Venture capital and private equity fund investments | Non-marketable securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Unrealized Gains (Losses) [Line Items]
Unrealized (losses) gains included in earnings attributable to Level 3 assets still held	22,845		75,576
Investment company fair value accounting | Other venture capital investments | Non-marketable securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Unrealized Gains (Losses) [Line Items]
Unrealized (losses) gains included in earnings attributable to Level 3 assets still held	13,770		14,076
Investment company fair value accounting | Other investments | Non-marketable securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Unrealized Gains (Losses) [Line Items]
Unrealized (losses) gains included in earnings attributable to Level 3 assets still held	(16)		4
Investment company fair value accounting | Non-marketable securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Unrealized Gains (Losses) [Line Items]
Unrealized (losses) gains included in earnings attributable to Level 3 assets still held	36,599	[1]	89,656	[1]
Equity warrant assets | Other assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Unrealized Gains (Losses) [Line Items]
Unrealized (losses) gains included in earnings attributable to Level 3 assets still held	$ 3,288	[2]	$ 11,297	[2]

[1] Unrealized gains are recorded on the line items gains on investment securities, net and other noninterest income, components of noninterest income.

[2] Unrealized gains are recorded on the line item gains on derivative instruments, net a component of noninterest income.