Major Components of Investment Securities Portfolio (Parenthetical) (Detail) (USD $)																					9 Months Ended	12 Months Ended	9 Months Ended		12 Months Ended		9 Months Ended		12 Months Ended		9 Months Ended				12 Months Ended		9 Months Ended			12 Months Ended		9 Months Ended				12 Months Ended		9 Months Ended			12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended			9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	1 Months Ended	9 Months Ended		12 Months Ended				9 Months Ended	12 Months Ended	3 Months Ended	9 Months Ended		9 Months Ended
	Sep. 30, 2012 Fair value accounting Other venture capital investments		Dec. 31, 2011 Fair value accounting Other venture capital investments		Sep. 30, 2012 Fair value accounting Other investments	Dec. 31, 2011 Fair value accounting Other investments	Sep. 30, 2012 Fair value accounting Venture capital and private equity fund investments		Dec. 31, 2011 Fair value accounting Venture capital and private equity fund investments		Sep. 30, 2012 Equity method accounting Other investments		Dec. 31, 2011 Equity method accounting Other investments		Sep. 30, 2012 Cost method accounting Other investments	Dec. 31, 2011 Cost method accounting Other investments	Sep. 30, 2012 Cost method accounting Venture capital and private equity fund investments Investment		Dec. 31, 2011 Cost method accounting Venture capital and private equity fund investments Investment		Sep. 30, 2012 SVB Capital-NT Growth Partners, LP Fair value accounting Venture capital and private equity fund investments	Dec. 31, 2011 SVB Capital-NT Growth Partners, LP Fair value accounting Venture capital and private equity fund investments	Sep. 30, 2012 SVB Capital Partners II, LP Fair value accounting Other venture capital investments		Dec. 31, 2011 SVB Capital Partners II, LP Fair value accounting Other venture capital investments		Sep. 30, 2012 SVB Capital Partners II, LP Fair value accounting Venture capital and private equity fund investments		Dec. 31, 2011 SVB Capital Partners II, LP Fair value accounting Venture capital and private equity fund investments		Sep. 30, 2012 SVB Capital Partners II, LP Fair value accounting Direct ownership interest Venture capital and private equity fund investments	Sep. 30, 2012 SVB Capital Partners II, LP Fair value accounting Indirect ownership interest Venture capital and private equity fund investments	Sep. 30, 2012 Other private equity fund Fair value accounting Venture capital and private equity fund investments		Dec. 31, 2011 Other private equity fund Fair value accounting Venture capital and private equity fund investments		Sep. 30, 2012 Other private equity fund Fair value accounting Direct ownership interest Venture capital and private equity fund investments	Sep. 30, 2012 Gold Hill Venture Lending 03, LP Equity method accounting Other investments		Dec. 31, 2011 Gold Hill Venture Lending 03, LP Equity method accounting Other investments		Sep. 30, 2012 Gold Hill Venture Lending 03, LP Equity method accounting Direct ownership interest Other investments	Sep. 30, 2012 Gold Hill Venture Lending 03, LP Equity method accounting Indirect ownership interest Other investments	Sep. 30, 2012 Gold Hill Capital 2008, LP Equity method accounting Other investments		Dec. 31, 2011 Gold Hill Capital 2008, LP Equity method accounting Other investments		Sep. 30, 2012 Gold Hill Capital 2008, LP Equity method accounting Direct ownership interest Other investments	Sep. 30, 2012 Gold Hill Capital 2008, LP Equity method accounting Indirect ownership interest Other investments	Sep. 30, 2012 SVB Strategic Investors Fund, LP Fair value accounting Venture capital and private equity fund investments	Dec. 31, 2011 SVB Strategic Investors Fund, LP Fair value accounting Venture capital and private equity fund investments	Sep. 30, 2012 SVB Strategic Investors Fund II, LP Fair value accounting Venture capital and private equity fund investments	Dec. 31, 2011 SVB Strategic Investors Fund II, LP Fair value accounting Venture capital and private equity fund investments	Sep. 30, 2012 SVB Strategic Investors Fund III, LP Fair value accounting Venture capital and private equity fund investments	Dec. 31, 2011 SVB Strategic Investors Fund III, LP Fair value accounting Venture capital and private equity fund investments	Sep. 30, 2012 SVB Strategic Investors Fund IV, LP Fair value accounting Venture capital and private equity fund investments	Dec. 31, 2011 SVB Strategic Investors Fund IV, LP Fair value accounting Venture capital and private equity fund investments	Dec. 31, 2011 Strategic Investors Fund V, LP Fair value accounting Venture capital and private equity fund investments	Sep. 30, 2012 Strategic Investors Fund V, LP Fair value accounting Venture capital and private equity fund investments	Sep. 30, 2012 SVB Capital Preferred Return Fund, LP Fair value accounting Venture capital and private equity fund investments	Dec. 31, 2011 SVB Capital Preferred Return Fund, LP Fair value accounting Venture capital and private equity fund investments	Sep. 30, 2012 Silicon Valley BancVentures, LP Fair value accounting Other venture capital investments	Dec. 31, 2011 Silicon Valley BancVentures, LP Fair value accounting Other venture capital investments	Sep. 30, 2012 SVB India Capital Partners I, LP Fair value accounting Other venture capital investments	Dec. 31, 2011 SVB India Capital Partners I, LP Fair value accounting Other venture capital investments	Sep. 30, 2012 SVB Capital Shanghai Yangpu Venture Capital Fund Fair value accounting Other venture capital investments	Dec. 31, 2011 SVB Capital Shanghai Yangpu Venture Capital Fund Fair value accounting Other venture capital investments	Sep. 30, 2012 Partners for Growth II, LP Equity method accounting Other investments	Dec. 31, 2011 Partners for Growth II, LP Equity method accounting Other investments	May 03, 2012 China Joint Venture Investment Equity method accounting Other investments	Sep. 30, 2012 China Joint Venture Investment Equity method accounting Other investments		Dec. 31, 2011 China Joint Venture Investment Equity method accounting Other investments		Sep. 30, 2012 Other investment Equity method accounting Other investments	Dec. 31, 2011 Other investment Equity method accounting Other investments	Sep. 30, 2012 Upper Limit Cost method accounting Venture capital and private equity fund investments	Dec. 31, 2011 Upper Limit Cost method accounting Venture capital and private equity fund investments	Sep. 30, 2012 Other Than Temporarily Impaired Securities Cost method accounting Venture capital and private equity fund investments	Sep. 30, 2012 Other Than Temporarily Impaired Securities Cost method accounting Venture capital and private equity fund investments Investment	Sep. 30, 2012 Estimated Fair Value Cost method accounting Venture capital and private equity fund investments	Sep. 30, 2012 SVB Capital-NT Growth Partners, LP Other private equity fund Fair value accounting Indirect ownership interest Venture capital and private equity fund investments	Sep. 30, 2012 SVB Capital Preferred Return Fund, LP Other private equity fund Fair value accounting Indirect ownership interest Venture capital and private equity fund investments
Investment Holdings [Line Items]
Non-marketable securities	$ 118,622,000	[1]	$ 124,121,000	[1]	$ 0	$ 987,000	$ 658,409,000	[2]	$ 611,824,000	[2]											$ 61,253,000	$ 43,958,000	$ 55,686,000	[3]	$ 61,099,000	[3]	$ 1,341,000	[4]	$ 2,390,000	[4]			$ 6,291,000	[5]	$ 11,367,000	[5]														$ 35,963,000	$ 39,567,000	$ 103,302,000	$ 122,619,000	$ 208,809,000	$ 218,429,000	$ 161,082,000	$ 122,076,000	$ 8,838,000	$ 28,908,000	$ 51,460,000	$ 42,580,000	$ 16,737,000	$ 17,878,000	$ 42,713,000	$ 42,832,000	$ 3,486,000	$ 2,312,000
Percentage of ownership																					33.00%	33.00%	5.10%	[3]	5.10%	[3]	5.10%	[4]	5.10%	[4]	1.30%	3.80%	58.20%	[5]	58.20%	[5]	41.50%	9.30%	[6]	9.30%	[6]	4.80%	4.50%	15.50%	[7]	15.50%	[7]	11.50%	4.00%	12.60%	12.60%	8.60%	8.60%	5.90%	5.90%	5.00%	5.00%	0.30%		20.00%	20.00%	10.70%	10.70%	14.40%	14.40%	6.80%	6.80%	24.20%	24.20%		50.00%	[8]	0.00%	[8]			5.00%	5.00%				12.60%	4.10%
Non-marketable securities											141,761,000	[9]	68,252,000	[9]																								9,187,000	[6]	16,072,000	[6]			20,491,000	[7]	19,328,000	[7]																					3,199,000	3,785,000		78,484,000	[8]	0	[8]	30,400,000	29,067,000
Contribution in joint venture																																																																						79,700,000
Number of investments																	325		329
Recognized other-than-temporary impairment (OTTI) losses																																																																															400,000	900,000
Number of impaired investments																																																																																43
Non-marketable securities															$ 19,942,000	$ 19,355,000	$ 158,275,000	[10]	$ 145,007,000	[10]																																																													$ 190,000,000

[1] The following table shows the amounts of other venture capital investments held by the following consolidated funds and our ownership percentage of each fund at September 30, 2012 and December 31, 2011 (fair value accounting): September 30, 2012 December 31, 2011(Dollars in thousands) Amount Ownership % Amount Ownership %Silicon Valley BancVentures, LP $16,737 10.7% $17,878 10.7%SVB Capital Partners II, LP (i) 55,686 5.1 61,099 5.1SVB India Capital Partners I, LP 42,713 14.4 42,832 14.4SVB Capital Shanghai Yangpu Venture Capital Fund 3,486 6.8 2,312 6.8Total other venture capital investments $118,622 $124,121

[2] The following table shows the amounts of venture capital and private equity fund investments held by the following consolidated funds and our ownership percentage of each fund at September 30, 2012 and December 31, 2011 (fair value accounting):

[3] At September 30, 2012, we had a direct ownership interest of 1.3 percent and an indirect ownership interest of 3.8 percent in the fund through our ownership of SVB Strategic Investors Fund II, LP.

[4] At September 30, 2012, we had a direct ownership interest of 1.3 percent and an indirect ownership interest of 3.8 percent in the fund through our ownership interest of SVB Strategic Investors Fund II, LP.

[5] At September 30, 2012, we had a direct ownership interest 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

[6] At September 30, 2012, 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 3, LLC (“GHLLC”) of 4.5 percent.

[7] At September 30, 2012, we had a direct ownership interest of 11.5 percent in the fund and an indirect interest in the fund through our investment in Gold Hill Capital 2008, LLC of 4.0 percent.

[8] On May 3, 2012, we contributed $79.7 million to SPD Silicon Valley Bank Co., Ltd. ("SPD-SVB"), our joint venture bank in China.

[9] The following table shows the carrying value and our ownership percentage of each investment at September 30, 2012 and December 31, 2011 (equity method accounting): September 30, 2012 December 31, 2011(Dollars in thousands) Amount Ownership % Amount Ownership %Gold Hill Venture Lending 03, LP (i) $9,187 9.3% $16,072 9.3%Gold Hill Capital 2008, LP (ii) 20,491 15.5 19,328 15.5Partners for Growth II, LP 3,199 24.2 3,785 24.2China Joint Venture investment (iii) 78,484 50.0 — —Other investments 30,400 N/A 29,067 N/A Total other investments (equity method accounting) $141,761 $68,252

[10] Represents investments in 325 and 329 funds (primarily venture capital funds) at September 30, 2012 and December 31, 2011, respectively, where our ownership interest is less than 5% of the voting interests of each such fund and in which we do not have the ability to exercise significant influence over the partnerships operating activities and financial policies. For the three months ended September 30, 2012, we recognized OTTI losses of $0.4 million resulting from other-than-temporary declines in value for 17 of the 325 investments. For the nine months ended September 30, 2012, we recognized OTTI losses of $0.9 million resulting from other-than-temporary declines in value for 43 of the 325 investments. The OTTI losses are included in net gains on investment securities, a component of noninterest income. We concluded that any declines in value for the remaining investments were temporary and as such, no OTTI was required to be recognized. At September 30, 2012, the carrying value of these venture capital and private equity fund investments (cost method accounting) was $158.3 million, and the estimated fair value was $190.0 million.