Regulatory Matters Capital Ratios for Company and Bank under Federal Regulatory Guidelines, Compared to Minimum Regulatory Capital Requirements for Adequately Capitalized and Well Capitalized Depository Institution (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
SVB Financial Group
CET 1 risk-based capital, actual ratio	12.78%	12.80%
CET 1 risk-based capital, well capitalized minimum ratio	6.50%	6.50%
CET 1 risk-based capital, adequately capitalized minimum ratio	4.50%	4.50%
CET 1 risk-based capital, actual amount	$ 4,182,315,000	$ 3,616,404,000
CET 1 risk-based capital, well capitalized minimum amount	2,127,902,000	1,836,169,000
CET 1 risk-based capital, adequately capitalized minimum amount	$ 1,473,163,000	$ 1,271,194,000
Tier 1 risk-based capital, actual ratio	12.97%	13.26%
Tier 1 risk-based capital, well capitalized minimum ratio	8.00%	8.00%
Tier 1 risk-based capital, adequately capitalized minimum ratio	6.00%	6.00%
Tier 1 risk-based capital, actual amount	$ 4,246,606,000	$ 3,744,605,000
Tier 1 risk-based capital, well capitalized minimum amount	2,618,957,000	2,259,900,000
Tier 1 risk-based capital, adequately capitalized minimum amount	$ 1,964,218,000	$ 1,694,925,000
Total risk-based capital, actual ratio	13.96%	14.21%
Total risk-based capital, well capitalized minimum ratio	10.00%	10.00%
Total risk-based capital, adequately capitalized minimum ratio	8.00%	8.00%
Total risk-based capital, actual amount	$ 4,571,542,000	$ 4,015,236,000
Total risk-based capital, well capitalized minimum amount	3,273,696,000	2,824,875,000
Total risk-based capital, adequately capitalized minimum amount	$ 2,618,957,000	$ 2,259,900,000
Tier 1 leverage, actual ratio	8.34%	8.34%
Tier 1 leverage, adequately capitalized minimum ratio	4.00%	4.00%
Tier 1 leverage, actual amount	$ 4,246,606,000	$ 3,744,605,000
Tier 1 leverage, adequately capitalized minimum amount	$ 2,036,138,000	$ 1,796,387,000
Silicon Valley Bank
CET 1 risk-based capital, actual ratio	12.06%	12.65%
CET 1 risk-based capital, well capitalized minimum ratio	6.50%	650.00%
CET 1 risk-based capital, adequately capitalized minimum ratio	4.50%	450.00%
CET 1 risk-based capital, actual amount	$ 3,787,988,000	$ 3,397,232,000
CET 1 risk-based capital, well capitalized minimum amount	2,041,227,000	1,745,695,000
CET 1 risk-based capital, adequately capitalized minimum amount	$ 1,413,157,000	$ 1,208,558,000
Tier 1 risk-based capital, actual ratio	12.06%	12.65%
Tier 1 risk-based capital, well capitalized minimum ratio	8.00%	8.00%
Tier 1 risk-based capital, adequately capitalized minimum ratio	6.00%	6.00%
Tier 1 risk-based capital, actual amount	$ 3,787,988,000	$ 3,397,232,000
Tier 1 risk-based capital, well capitalized minimum amount	2,512,279,000	2,148,548,000
Tier 1 risk-based capital, adequately capitalized minimum amount	$ 1,884,209,000	$ 1,611,411,000
Total risk-based capital, actual ratio	13.04%	13.66%
Total risk-based capital, well capitalized minimum ratio	10.00%	10.00%
Total risk-based capital, adequately capitalized minimum ratio	8.00%	8.00%
Total risk-based capital, actual amount	$ 4,094,782,000	$ 3,667,709,000
Total risk-based capital, well capitalized minimum amount	3,140,349,000	2,685,685,000
Total risk-based capital, adequately capitalized minimum amount	$ 2,512,279,000	$ 2,148,548,000
Tier 1 leverage, actual ratio	7.56%	7.67%
Tier 1 leverage, well capitalized minimum ratio	5.00%	5.00%
Tier 1 leverage, adequately capitalized minimum ratio	4.00%	4.00%
Tier 1 leverage, actual amount	$ 3,787,988,000	$ 3,397,232,000
Tier 1 leverage, well capitalized minimum amount	2,504,636,000	2,214,467,000
Tier 1 leverage, adequately capitalized minimum amount	$ 2,003,709,000	$ 1,771,574,000