Fair Value of Financial Instruments - Quantitative Information About Significant Unobservable Inputs (Detail) (USD $) In Thousands, unless otherwise specified													3 Months Ended			3 Months Ended							3 Months Ended						3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2014 Equity warrant assets Other assets		Dec. 31, 2013 Equity warrant assets Other assets		Mar. 31, 2013 Equity warrant assets Other assets		Dec. 31, 2012 Equity warrant assets Other assets		Mar. 31, 2014 Level 3 Other venture capital investments Fair value accounting	Mar. 31, 2013 Level 3 Other venture capital investments Fair value accounting	Dec. 31, 2013 Level 3 Other venture capital investments Fair value accounting	Mar. 31, 2014 Level 3 Other securities Fair value accounting		Mar. 31, 2013 Level 3 Other securities Fair value accounting		Dec. 31, 2013 Level 3 Other securities Fair value accounting	Mar. 31, 2014 Level 3 Equity warrant assets Investments [Member]	Dec. 31, 2013 Level 3 Equity warrant assets Investments [Member]	Mar. 31, 2014 Level 3 Equity warrant assets Other assets		Mar. 31, 2013 Level 3 Equity warrant assets Other assets		Mar. 31, 2014 Level 3 Equity Warrant Asset, Private Portfolio [Member] Investments [Member]	Dec. 31, 2013 Level 3 Equity Warrant Asset, Private Portfolio [Member] Investments [Member]	Mar. 31, 2014 Level 3 Equity Warrant Asset, Private Portfolio [Member] Other assets		Mar. 31, 2013 Level 3 Equity Warrant Asset, Private Portfolio [Member] Other assets		Mar. 31, 2014 Fair Value, Measurements, Recurring Other securities Fair value accounting		Dec. 31, 2013 Fair Value, Measurements, Recurring Other securities Fair value accounting
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	$ 1,455,357	$ 1,314,951	$ 891,908	$ 859,141	$ 87,642	[1]	$ 99,891	[1]	$ 66,046	[1]	$ 66,129	[1]	$ 28,306		$ 32,839	$ 362,487				$ 319,249	$ 9,128	$ 24,217					$ 78,514	$ 75,674					$ 362,487	[2]	$ 319,249	[2]
Fair Value Inputs, Weighted Average Discount for Sales Restrictions																10.10%	[3]	12.00%	[3]				14.10%	[3]	13.70%	[3]
Valuation Technique													Private company equity pricing	Private company equity pricing		Modified stock price		Modified stock price					Modified Black-Scholes option pricing model		Modified Black-Scholes option pricing model				Modified Black-Scholes option pricing model		Modified Black-Scholes option pricing model
Volatility																							42.30%		41.30%				39.80%		40.10%
Risk-Free interest rate																							1.90%		1.70%				0.80%		0.80%
Marketability discount																													22.50%	[4]	22.50%	[4]
Remaining life assumption																													45.00%	[5]	45.00%	[5]

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

[2] Ending balance Includes total unrealized valuation gains of $351 million attributable to two of our portfolio companies, FireEye and Twitter.

[3] We adjust quoted market prices of public companies, which are subject to certain sales restrictions. Sales restriction discounts generally range from 10 percent to 20 percent depending on the duration of the sales restrictions, which typically range from 3 to 6 months.

[4] Our marketability discount is applied to all private company warrants to account for a general lack of liquidity due to the private nature of the associated underlying company. The quantitative measure used is based on long-run averages and is influenced over time by various factors, including market conditions. On a quarterly basis, a sensitivity analysis is performed on our marketability discount.

[5] We adjust the contractual remaining term of private company warrants based on our estimate of the actual remaining life, which we determine by utilizing historical data on cancellations and exercises. At March 31, 2014, the weighted average contractual remaining term was 6.2 years, compared to our estimated remaining life of 2.8 years. On a quarterly basis, a sensitivity analysis is performed on our remaining life assumption.