Fair Value of Financial Instruments - Unrealized Gains Included in Earnings Attributable to Level 3 Assets Held (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Unrealized Gains (Losses) [Line Items]
Unrealized gains included in earnings attributable to Level 3 assets still held	$ 24,328		$ 10,734
Unrealized gains attributable to noncontrolling interests	21,187		7,242
Equity warrant assets | Other assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Unrealized Gains (Losses) [Line Items]
Unrealized gains included in earnings attributable to Level 3 assets still held	1,181	[1]	1,674	[1]
Non-marketable securities | Fair value accounting
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Unrealized Gains (Losses) [Line Items]
Unrealized gains included in earnings attributable to Level 3 assets still held	23,147	[2]	9,060	[2]
Non-marketable securities | Fair value accounting | Venture capital and private equity fund investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Unrealized Gains (Losses) [Line Items]
Unrealized gains included in earnings attributable to Level 3 assets still held	22,621		11,649
Non-marketable securities | Fair value accounting | Other venture capital investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Unrealized Gains (Losses) [Line Items]
Unrealized gains included in earnings attributable to Level 3 assets still held	526		(2,610)
Non-marketable securities | Fair value accounting | Other investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Unrealized Gains (Losses) [Line Items]
Unrealized gains included in earnings attributable to Level 3 assets still held	$ 0		$ 21

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

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