Off-Balance Sheet Arrangements, Guarantees and Other Commitments - Total Capital Commitments, Unfunded Capital Commitments, and Our Ownership in Each Fund (Additional Information) (Detail) - Consolidated venture capital and private equity fund investments	3 Months Ended
	Mar. 31, 2018 Investment
Other fund investments
Venture Capital and Private Equity Fund Investments [Line Items]
Number of other funds with investment commitments	229
Other fund investments | Upper Limit
Venture Capital and Private Equity Fund Investments [Line Items]
Percentage of ownership	5.00%
Fair value accounting | Direct ownership interest | SVB Capital Partners II, LP
Venture Capital and Private Equity Fund Investments [Line Items]
Percentage of ownership	1.30%
Fair value accounting | Indirect ownership interest | SVB Capital Partners II, LP
Venture Capital and Private Equity Fund Investments [Line Items]
Percentage of ownership	3.80%