Parent Company Only Condensed Financial Information - Condensed Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets:
Cash and cash equivalents	$ 17,674,763	$ 6,781,783
Investment securities	49,306,826	29,071,694
Loans, amortized cost	45,181,488	33,164,636
Lease right-of-use assets	209,932	197,365
Other assets	3,205,825	1,745,233
Total assets	115,511,007	71,004,903
Liabilities and total equity
Lease liabilities	259,554	218,847
Other liabilities	3,971,974	2,041,752
Total liabilities	107,077,516	64,383,823
SVBFG stockholders' equity	8,219,700	6,470,307
Total liabilities and total equity	115,511,007	71,004,903
Parent Company
Assets:
Cash and cash equivalents	670,738	800,926
Investment securities	666,860	474,842
Loans, amortized cost	682	15,245
Lease right-of-use assets	99,363	71,847
Other assets	260,331	214,167
Total assets	9,433,935	7,043,195
Liabilities and total equity
Lease liabilities	134,607	87,999
Other liabilities	236,000	136,903
Total liabilities	1,214,235	572,889
SVBFG stockholders' equity	8,219,700	6,470,306
Total liabilities and total equity	9,433,935	7,043,195
Parent Company | 3.125% Senior Notes
Liabilities and total equity
Senior Notes	495,280	0
Parent Company | 3.50% Senior Notes
Liabilities and total equity
Senior Notes	348,348	347,987
Parent Company | Bank Subsidiary
Assets:
Investment in subsidiaries	7,068,964	5,034,095
Parent Company | Nonbank Subsidiaries
Assets:
Investment in subsidiaries	$ 666,997	$ 432,073