Investment Securities - Non-marketable and Other Securities (Detail) $ in Thousands		3 Months Ended		9 Months Ended		12 Months Ended
		Sep. 30, 2015 USD ($) Investment	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) Investment	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($) Investment	Sep. 30, 2014 Investment
Investment Holdings [Line Items]
Total non-marketable and other securities	[1]	$ 650,555		$ 650,555		$ 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		$ 779		$ 779		$ 108,251
Venture capital and private equity fund investments
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting		84,197		84,197
Venture capital and private equity fund investments | SVB Strategic Investors Fund II, LP
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting		11,204		11,204
Venture capital and private equity fund investments | SVB Strategic Investors Fund III, LP
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting		24,781		24,781
Venture capital and private equity fund investments | SVB Strategic Investors Fund IV, LP
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting		25,542		25,542
Venture capital and private equity fund investments | Other investments
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting		22,670		22,670
Venture capital and private equity fund investments | Fair value accounting
Investment Holdings [Line Items]
Non-marketable securities, fair value accounting		154,660		154,660		1,130,882
Non-marketable securities, cost method accounting		244,000		244,000		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		23,229		$ 23,229		$ 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		61,869		$ 61,869		$ 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		62,818		$ 62,818		$ 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		6,744		$ 6,744		$ 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		84,197		$ 84,197		$ 0
Venture capital and private equity fund investments | Cost method accounting
Investment Holdings [Line Items]
Non-marketable securities, cost method accounting		$ 123,550		$ 123,550		$ 140,551
Number of investments		270	281	270	281	281	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		21,217		21,217		$ 26,672
Debt funds | Equity method accounting | Gold Hill Capital 2008, LP
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting		17,662		$ 17,662		$ 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		3,555		$ 3,555		$ 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		119,731		$ 119,731		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		79,299		$ 79,299		$ 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		40,432		$ 40,432		$ 36,433
Other investments | Cost method accounting
Investment Holdings [Line Items]
Non-marketable securities, cost method accounting		17,499		17,499		13,423
Low Income Housing Tax Credit Funds
Investment Holdings [Line Items]
Nonmarketable securities, other		125,532		125,532		121,155
Tax credits and other tax benefits recognized		4,780	$ 3,087	11,207	$ 9,312
Amortization expense included in provision for income taxes		2,011	$ 1,246	7,549	$ 5,971
Unfunded commitments
Investment Holdings [Line Items]
Accrued expenses and other liabilities		$ 65,305		$ 65,305		$ 65,921

[1] Prior period amounts have been revised to reflect the retrospective application of new accounting guidance adopted in the first quarter of 2015 related to our investments in qualified affordable housing projects (ASU 2014-01). See Note 1— "Basis of Presentation" of the "Notes to Interim Consolidated Financial Statements" under Part I, Item 1 in this report.