Fair Value of Financial Instruments - Quantitative Information About Significant Unobservable Inputs (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2013		Dec. 31, 2012		Jun. 30, 2013		Sep. 30, 2012		Jun. 30, 2012		Dec. 31, 2011
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	$ 1,134,038		$ 859,141		$ 938,244		$ 841,722		$ 828,326		$ 799,962
Other venture capital investments | Fair value accounting
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	55,359		127,091
Valuation Technique	Private company equity pricing		Private company equity pricing
Equity warrant assets (public portfolio) | Investments [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	12,618
Equity warrant assets (private portfolio) | Investments [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	75,508		66,129
Equity warrant assets | Other assets
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	88,126	[1]	66,129		73,229	[1]	64,691	[1]	68,619	[1]	63,030
Valuation Technique	Modified Black-Scholes option pricing model		Modified Black-Scholes option pricing model
Volatility	39.70%	[2]	45.20%	[2]
Risk-Free interest rate	0.80%	[2]	0.40%	[2]
Marketability discount	22.50%	[2],[3]	22.50%	[2],[3]
Remaining life assumption	45.00%	[2],[4]	45.00%	[2],[4]
Fair Value, Measurements, Recurring | Other Securities [Member] | Fair value accounting
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	217,054		0		0
Fair Value, Measurements, Recurring | Level 3 | Other Securities [Member] | Fair value accounting
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	$ 217,054

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

[2] In determining the fair value of our other venture capital investment portfolio, we evaluate a variety of factors related to each underlying private portfolio company including, but not limited to, actual and forecasted results, cash position, recent or planned transactions and market comparable companies. Additionally, we have ongoing communication with the portfolio companies and venture capital fund managers, to determine whether there is a material change in fair value. These factors are specific to each portfolio company and a weighted average or range of values of the unobservable inputs is not meaningful.

[3] Our ownership includes direct ownership of 41.5 percent and indirect ownership interests of 12.6 percent and 4.1 percent in the fund through our ownership interest of SVB Capital - NT Growth Partners, LP and SVB Capital Preferred Return Fund, LP, respectively.

[4] At September 30, 2013, we had a direct ownership interest of 4.8 percent in the fund and an indirect interest in the fund through our investment in Gold Hill Venture Lending Partners 03, LLC (“GHLLC”) of 4.5 percent.