Junior Subordinated Debentures Issued to Capital Trusts - Additional Information (Detail) - USD ($)		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014
Subordinated Borrowing [Line Items]
Junior subordinated debentures issued to capital trusts		$ 41,414,000		$ 41,252,000
Maximum allowable period of interest deferment		5 years
Trust Preferred Securities Subject to Mandatory Redemption [Member]
Subordinated Borrowing [Line Items]
Percentage of trust preferred securities disallowed for Tier 1 capital treatment		75.00%
GCB Capital Trust III [Member] | Subordinated Debentures Subject to Mandatory Redemption [Member]
Subordinated Borrowing [Line Items]
Debt instrument percentage	[1]	6.96%
Junior subordinated debentures issued to capital trusts		$ 24,846,000	[2]	24,900,000
Contractual principal balances		$ 24,743,000		24,700,000
GCB Capital Trust III [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member]
Subordinated Borrowing [Line Items]
Debt instrument percentage	[1]	6.96%
Face value		$ 24,000,000		24,000,000
State Bancorp Capital Trust I [Member] | Subordinated Debentures Subject to Mandatory Redemption [Member]
Subordinated Borrowing [Line Items]
Junior subordinated debentures issued to capital trusts		8,624,000	[2]	8,500,000
Contractual principal balances		10,310,000		10,300,000
State Bancorp Capital Trust I [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member]
Subordinated Borrowing [Line Items]
Face value		10,000,000		10,000,000
State Bancorp Capital Trust II [Member] | Subordinated Debentures Subject to Mandatory Redemption [Member]
Subordinated Borrowing [Line Items]
Junior subordinated debentures issued to capital trusts		7,944,000	[2]	7,800,000
Contractual principal balances		10,310,000		10,300,000
State Bancorp Capital Trust II [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member]
Subordinated Borrowing [Line Items]
Face value		$ 10,000,000		$ 10,000,000

[1] 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.

[2] 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.