Junior Subordinated Debentures Issued to Capital Trusts - Schedule of Outstanding Junior Subordinated Debentures and Related Trust Preferred Securities Issued by Each Trust (Detail) - USD ($)		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Carrying value		$ 41,414,000		$ 41,252,000
GCB Capital Trust III [Member]
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Annual interest rate, base rate		3-month LIBOR
Annual interest rate spread, percentage		1.40%
Subordinated Debentures Subject to Mandatory Redemption [Member] | GCB Capital Trust III [Member]
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Carrying value		$ 24,846,000	[1]	24,900,000
Contractual principal balance		$ 24,743,000		24,700,000
Annual interest rate	[2]	6.96%
Stated maturity date		Jul. 30, 2037
Initial call date		Jul. 30, 2017
Subordinated Debentures Subject to Mandatory Redemption [Member] | State Bancorp Capital Trust I [Member]
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Carrying value		$ 8,624,000	[1]	8,500,000
Contractual principal balance		$ 10,310,000		10,300,000
Annual interest rate, base rate	[2]	3-month LIBOR
Annual interest rate spread, percentage	[2]	3.45%
Stated maturity date		Nov. 07, 2032
Initial call date		Nov. 07, 2007
Subordinated Debentures Subject to Mandatory Redemption [Member] | State Bancorp Capital Trust II [Member]
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Carrying value		$ 7,944,000	[1]	7,800,000
Contractual principal balance		$ 10,310,000		10,300,000
Annual interest rate, base rate	[2]	3-month LIBOR
Annual interest rate spread, percentage	[2]	2.85%
Stated maturity date		Jan. 23, 2034
Initial call date		Jan. 23, 2009
Trust Preferred Securities Subject to Mandatory Redemption [Member] | GCB Capital Trust III [Member]
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Face value		$ 24,000,000		24,000,000
Annual interest rate	[2]	6.96%
Issuance date		Jul. 02, 2007
Distribution dates	[3]	Quarterly
Trust Preferred Securities Subject to Mandatory Redemption [Member] | State Bancorp Capital Trust I [Member]
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Face value		$ 10,000,000		10,000,000
Annual interest rate, base rate	[2]	3-month LIBOR
Annual interest rate spread, percentage	[2]	3.45%
Issuance date		Oct. 29, 2002
Distribution dates	[3]	Quarterly
Trust Preferred Securities Subject to Mandatory Redemption [Member] | State Bancorp Capital Trust II [Member]
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Face value		$ 10,000,000		$ 10,000,000
Annual interest rate, base rate	[2]	3-month LIBOR
Annual interest rate spread, percentage	[2]	2.85%
Issuance date		Dec. 19, 2003
Distribution dates	[3]	Quarterly

[1] The carrying value for GCB Capital Trust III includes an unamortized purchase accounting premium of $103 thousand, and the carrying values for State Bancorp Capital Trust I and State Bancorp Capital Trust II include purchase accounting discounts of $1.7 million and $2.4 million, respectively.

[2] Interest on GCB Capital Trust III is fixed until July 30, 2017, then resets to 3-month LIBOR plus 1.4 percent. The annual interest rate for all of the junior subordinated debentures and related trust preferred securities excludes the effect of the purchase accounting adjustments.

[3] All cash distributions are cumulative.