Investment Securities - Non-marketable and Other Securities (Detail) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017 USD ($) Investment	Sep. 30, 2016 USD ($) Investment	Sep. 30, 2017 USD ($) Investment	Sep. 30, 2016 USD ($) Investment	Dec. 31, 2016 USD ($) Investment
Investment Holdings [Line Items]
Total non-marketable and other securities	$ 627,469		$ 627,469		$ 622,552
Upper Limit
Investment Holdings [Line Items]
Equity method investment voting ownership percentage	5.00%		5.00%
Fair value accounting
Investment Holdings [Line Items]
Non-marketable securities, fair value accounting	$ 392		$ 392		753
Venture capital and private equity fund investments | Fair value accounting
Investment Holdings [Line Items]
Non-marketable securities, fair value accounting	128,768		128,768		141,649
Non-marketable securities, cost method accounting	206,500		206,500		221,700
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	15,624		$ 15,624		$ 18,459
Percentage of ownership			12.60%		12.60%
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 | SVB Capital Preferred Return Fund, LP
Investment Holdings [Line Items]
Non-marketable securities, fair value accounting	55,685		$ 55,685		$ 57,627
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	57,459		$ 57,459		$ 59,718
Percentage of ownership			33.00%		33.00%
Venture capital and private equity fund investments | Fair value accounting | Other private equity fund
Investment Holdings [Line Items]
Non-marketable securities, fair value accounting	0		$ 0		$ 5,845
Percentage of ownership			0.00%		58.20%
Venture capital and private equity fund investments | Equity method accounting
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting	87,218		$ 87,218		$ 82,823
Venture capital and private equity fund investments | Equity method accounting | SVB Strategic Investors Fund II, LP
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting	6,084		$ 6,084		$ 7,720
Percentage of ownership			8.60%		8.60%
Venture capital and private equity fund investments | Equity method accounting | SVB Strategic Investors Fund III, LP
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting	19,292		$ 19,292		$ 20,449
Percentage of ownership			5.90%		5.90%
Venture capital and private equity fund investments | Equity method accounting | SVB Strategic Investors Fund IV, LP
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting	25,507		$ 25,507		$ 24,530
Percentage of ownership			5.00%		5.00%
Venture capital and private equity fund investments | Equity method accounting | Strategic Investors Fund V Funds
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting	14,987		$ 14,987		$ 12,029
Venture capital and private equity fund investments | Equity method accounting | SVB Capital Partners II, LP
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting	6,704		$ 6,704		$ 7,798
Percentage of ownership			5.10%		5.10%
Venture capital and private equity fund investments | Equity method accounting | Other investments
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting	14,644		$ 14,644		$ 10,297
Venture capital and private equity fund investments | Cost method accounting
Investment Holdings [Line Items]
Non-marketable securities, cost method accounting	$ 102,956		$ 102,956		$ 114,606
Number of investments | Investment	237	255	237	255	252
Other venture capital investments | Fair value accounting
Investment Holdings [Line Items]
Non-marketable securities, fair value accounting	$ 1,897		$ 1,897		$ 2,040
Other venture capital investments | Fair value accounting | Silicon Valley BancVentures, LP
Investment Holdings [Line Items]
Non-marketable securities, fair value accounting	1,897		$ 1,897		$ 2,040
Percentage of ownership			10.70%		10.70%
Debt funds | Equity method accounting
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting	17,889		$ 17,889		$ 17,020
Debt funds | Equity method accounting | Gold Hill Capital 2008, LP
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting	15,381		$ 15,381		$ 13,557
Percentage of ownership			15.50%		15.50%
Debt funds | Equity method accounting | Other investments
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting	2,508		$ 2,508		$ 3,463
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	113,478		$ 113,478		$ 123,514
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	75,511		$ 75,511		$ 75,296
Percentage of ownership			50.00%		50.00%
Other investments | Equity method accounting | Other investments
Investment Holdings [Line Items]
Non-marketable securities, equity method accounting	37,967		$ 37,967		$ 48,218
Other investments | Cost method accounting
Investment Holdings [Line Items]
Non-marketable securities, cost method accounting	26,835		26,835		$ 27,700
Low income housing tax credit funds
Investment Holdings [Line Items]
Affordable Housing Tax Credits and Other Tax Benefits, Amount	4,539	$ 3,995	13,199	$ 12,127
Amortization Method Qualified Affordable Housing Project Investments, Amortization	$ 3,533	$ 2,556	$ 10,154	$ 9,746