Junior Subordinated Debentures Issued to Capital Trusts - Schedule of Outstanding Junior Subordinated Debentures and Related Trust Preferred Securities Issued by Each Trust, Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($)
State Bancorp Capital Trust I [Member]
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Purchase accounting discounts	$ 1,700
State Bancorp Capital Trust II [Member]
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Purchase accounting discounts	2,400
GCB Capital Trust III [Member]
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Unamortized purchase accounting premium	$ 103
Annual interest rate spread, percentage	1.40%