Off-Balance Sheet Arrangements, Guarantees and Other Commitments - Total Capital Commitments, Unfunded Capital Commitments, and Our Ownership in Each Fund (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($)
Venture Capital and Private Equity Fund Investments [Line Items]
SVBFG Unfunded Commitments	$ 5,775
Strategic Investors Fund, LP
Venture Capital and Private Equity Fund Investments [Line Items]
SVBFG Unfunded Commitments	1,338
Capital Preferred Return Fund, LP
Venture Capital and Private Equity Fund Investments [Line Items]
SVBFG Unfunded Commitments	2,658
Growth Partners, LP
Venture Capital and Private Equity Fund Investments [Line Items]
SVBFG Unfunded Commitments	1,779
Parent Company
Venture Capital and Private Equity Fund Investments [Line Items]
SVBFG Capital Commitments	450,067
SVBFG Unfunded Commitments	15,607
Parent Company | CP I, LP
Venture Capital and Private Equity Fund Investments [Line Items]
SVBFG Capital Commitments	6,000
SVBFG Unfunded Commitments	$ 270
SVBFG Ownership of each Fund	10.70%
Parent Company | CP II, LP
Venture Capital and Private Equity Fund Investments [Line Items]
SVBFG Capital Commitments	$ 1,200
SVBFG Unfunded Commitments	$ 162
SVBFG Ownership of each Fund	5.10%
Parent Company | Shanghai Yangpu Venture Capital Fund (LP)
Venture Capital and Private Equity Fund Investments [Line Items]
SVBFG Capital Commitments	$ 844
SVBFG Unfunded Commitments	$ 0
SVBFG Ownership of each Fund	6.80%
Parent Company | Strategic Investors Fund, LP
Venture Capital and Private Equity Fund Investments [Line Items]
SVBFG Capital Commitments	$ 15,300
SVBFG Unfunded Commitments	$ 688
SVBFG Ownership of each Fund	12.60%
Parent Company | Strategic Investors Fund II, LP
Venture Capital and Private Equity Fund Investments [Line Items]
SVBFG Capital Commitments	$ 15,000
SVBFG Unfunded Commitments	$ 1,050
SVBFG Ownership of each Fund	8.60%
Parent Company | Strategic Investors Fund III, LP
Venture Capital and Private Equity Fund Investments [Line Items]
SVBFG Capital Commitments	$ 15,000
SVBFG Unfunded Commitments	$ 1,275
SVBFG Ownership of each Fund	5.90%
Parent Company | Strategic Investors Fund IV, LP
Venture Capital and Private Equity Fund Investments [Line Items]
SVBFG Capital Commitments	$ 12,239
SVBFG Unfunded Commitments	$ 2,325
SVBFG Ownership of each Fund	5.00%
Parent Company | Strategic Investors Fund V funds
Venture Capital and Private Equity Fund Investments [Line Items]
SVBFG Capital Commitments	$ 515
SVBFG Unfunded Commitments	131
Parent Company | Capital Preferred Return Fund, LP
Venture Capital and Private Equity Fund Investments [Line Items]
SVBFG Capital Commitments	12,688
SVBFG Unfunded Commitments	$ 0
SVBFG Ownership of each Fund	20.00%
Parent Company | Growth Partners, LP
Venture Capital and Private Equity Fund Investments [Line Items]
SVBFG Capital Commitments	$ 24,670
SVBFG Unfunded Commitments	$ 1,340
SVBFG Ownership of each Fund	33.00%
Parent Company | Debt funds (equity method accounting)
Venture Capital and Private Equity Fund Investments [Line Items]
SVBFG Capital Commitments	$ 48,443
SVBFG Unfunded Commitments	0
Parent Company | Other fund investments
Venture Capital and Private Equity Fund Investments [Line Items]
SVBFG Capital Commitments	298,168
SVBFG Unfunded Commitments	$ 8,366