Investment Securities - Non-marketable and Other Securities (Detail) $ in Thousands		3 Months Ended		6 Months Ended		12 Months Ended
		Jun. 30, 2015 USD ($) Investment	Jun. 30, 2014 USD ($) Investment	Jun. 30, 2015 USD ($) Investment	Jun. 30, 2014 USD ($) Investment	Dec. 31, 2014 USD ($) Investment
Investment Holdings [Line Items]
Total non-marketable and other securities	[1]	$ 645,506		$ 645,506		$ 1,728,140
Ownership interest percentage						5.00%
Upper Limit
Investment Holdings [Line Items]
Ownership interest percentage		5.00%		5.00%
Fair value accounting
Investment Holdings [Line Items]
Non-marketable securities, fair value accounting		$ 287		$ 287		$ 108,251
Venture capital and private equity fund investments
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting		78,574		78,574
Venture capital and private equity fund investments | SVB Strategic Investors Fund II, LP
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting		11,516		11,516
Venture capital and private equity fund investments | SVB Strategic Investors Fund III, LP
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting		23,945		23,945
Venture capital and private equity fund investments | SVB Strategic Investors Fund IV, LP
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting		25,465		25,465
Venture capital and private equity fund investments | Other investments
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting		17,648		17,648
Venture capital and private equity fund investments | Fair value accounting
Investment Holdings [Line Items]
Non-marketable securities, fair value accounting		156,730		156,730		1,130,882
Non-marketable securities, cost method accounting		236,000		236,000		234,000
Venture capital and private equity fund investments | Fair value accounting | SVB Strategic Investors Fund, LP
Investment Holdings [Line Items]
Non-marketable securities, fair value accounting		23,283		$ 23,283		$ 24,645
Percentage of ownership				12.60%		12.60%
Venture capital and private equity fund investments | Fair value accounting | SVB Strategic Investors Fund II, LP
Investment Holdings [Line Items]
Non-marketable securities, fair value accounting		0		$ 0		$ 97,250
Percentage of ownership				8.60%		8.60%
Venture capital and private equity fund investments | Fair value accounting | SVB Strategic Investors Fund III, LP
Investment Holdings [Line Items]
Non-marketable securities, fair value accounting		0		$ 0		$ 269,821
Percentage of ownership				5.90%		5.90%
Venture capital and private equity fund investments | Fair value accounting | SVB Strategic Investors Fund IV, LP
Investment Holdings [Line Items]
Non-marketable securities, fair value accounting		0		$ 0		$ 291,291
Percentage of ownership				5.00%		5.00%
Venture capital and private equity fund investments | Fair value accounting | Strategic Investors Fund V Funds
Investment Holdings [Line Items]
Non-marketable securities, fair value accounting		0		$ 0		$ 226,111
Venture capital and private equity fund investments | Fair value accounting | Strategic Investors Fund VI Funds
Investment Holdings [Line Items]
Non-marketable securities, fair value accounting		0		0		$ 89,605
Percentage of ownership						0.00%
Venture capital and private equity fund investments | Fair value accounting | SVB Capital Preferred Return Fund, LP
Investment Holdings [Line Items]
Non-marketable securities, fair value accounting		62,901		$ 62,901		$ 62,110
Percentage of ownership				20.00%		20.00%
Venture capital and private equity fund investments | Fair value accounting | SVB Capital—NT Growth Partners, LP
Investment Holdings [Line Items]
Non-marketable securities, fair value accounting		63,728		$ 63,728		$ 61,973
Percentage of ownership				33.00%		33.00%
Venture capital and private equity fund investments | Fair value accounting | SVB Capital Partners II, LP
Investment Holdings [Line Items]
Non-marketable securities, fair value accounting		0		$ 0		$ 302
Percentage of ownership						5.10%
Venture capital and private equity fund investments | Fair value accounting | SVB Capital Partners II, LP | Direct ownership interest
Investment Holdings [Line Items]
Percentage of ownership				1.30%
Venture capital and private equity fund investments | Fair value accounting | SVB Capital Partners II, LP | Indirect ownership interest
Investment Holdings [Line Items]
Percentage of ownership				3.80%
Venture capital and private equity fund investments | Fair value accounting | Other private equity fund
Investment Holdings [Line Items]
Non-marketable securities, fair value accounting		6,818		$ 6,818		$ 7,774
Percentage of ownership				58.20%		58.20%
Venture capital and private equity fund investments | Fair value accounting | Other private equity fund | Direct ownership interest
Investment Holdings [Line Items]
Percentage of ownership				41.50%
Venture capital and private equity fund investments | Equity method accounting
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting		78,574		$ 78,574		$ 0
Venture capital and private equity fund investments | Cost method accounting
Investment Holdings [Line Items]
Non-marketable securities, cost method accounting		$ 127,073		$ 127,073		$ 140,551
Number of investments | Investment		273	282	273	282	281
Other venture capital investments | Fair value accounting
Investment Holdings [Line Items]
Non-marketable securities, fair value accounting		$ 3,390		$ 3,390		$ 71,204
Other venture capital investments | Fair value accounting | SVB Capital Partners II, LP
Investment Holdings [Line Items]
Non-marketable securities, fair value accounting		0		$ 0		$ 20,481
Percentage of ownership				0.00%		5.10%
Other venture capital investments | Fair value accounting | Silicon Valley BancVentures, LP
Investment Holdings [Line Items]
Non-marketable securities, fair value accounting		3,390		$ 3,390		$ 3,291
Percentage of ownership				10.70%		10.70%
Other venture capital investments | Fair value accounting | Capital Partners III, LP
Investment Holdings [Line Items]
Non-marketable securities, fair value accounting		0		$ 0		$ 41,055
Percentage of ownership				0.00%		0.00%
Other venture capital investments | Fair value accounting | SVB Capital Shanghai Yangpu Venture Capital Fund
Investment Holdings [Line Items]
Non-marketable securities, fair value accounting		0		$ 0		$ 6,377
Percentage of ownership						6.80%
Debt funds | Equity method accounting
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting		22,313		22,313		$ 26,672
Debt funds | Equity method accounting | Gold Hill Capital 2008, LP
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting		18,730		$ 18,730		$ 21,294
Percentage of ownership				15.50%		15.50%
Debt funds | Equity method accounting | Other investments
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting		3,583		$ 3,583		$ 5,378
Other investments | Fair value accounting | SVB Capital Preferred Return Fund, LP | Indirect ownership interest
Investment Holdings [Line Items]
Percentage of ownership				4.10%
Other investments | Fair value accounting | SVB Capital—NT Growth Partners, LP | Indirect ownership interest
Investment Holdings [Line Items]
Percentage of ownership				12.60%
Other investments | Fair value accounting | Other private equity fund | Direct ownership interest
Investment Holdings [Line Items]
Percentage of ownership				41.50%
Other investments | Equity method accounting
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting		118,406		$ 118,406		116,002
Other investments | Equity method accounting | Gold Hill Capital 2008, LP | Direct ownership interest
Investment Holdings [Line Items]
Percentage of ownership				11.50%
Other investments | Equity method accounting | Gold Hill Capital 2008, LP | Indirect ownership interest
Investment Holdings [Line Items]
Percentage of ownership				4.00%
Other investments | Equity method accounting | China Joint Venture investment
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting		79,740		$ 79,740		$ 79,569
Percentage of ownership				50.00%		50.00%
Other investments | Equity method accounting | Other investments
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting		38,666		$ 38,666		$ 36,433
Other investments | Cost method accounting
Investment Holdings [Line Items]
Non-marketable securities, cost method accounting		16,189		16,189		13,423
Low Income Housing Tax Credit Funds
Investment Holdings [Line Items]
Tax Credits And Other Tax Benefits Recognized		3,214	$ 3,113	6,427	$ 6,225
Nonmarketable securities, other		122,544		122,544		121,155
Amortization Expense Included In Provision For Income Taxes		2,741	$ 2,347	5,538	$ 4,725
Unfunded commitments
Investment Holdings [Line Items]
Accrued expenses and other liabilities		$ 63,637		$ 63,637		$ 65,921

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