Junior Subordinated Debentures Issued to Capital Trusts - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2010
Schedule Of Outstanding Junior Subordinated Debentures And The Related Trust Preferred Securities Issued [Line Items]
Net trading gains and losses included in non-cash credits	$ 2,600,000		$ 1,300,000
Non-cash charges included in net trading gains and (losses)				5,800,000
Junior subordinated debentures issued to capital trusts	188,522,000		185,598,000
Maximum allowable period of interest deferment	5 years
Trust preferred securities phased out as Tier 1 capital, period one	3 years
Trust preferred securities phased out period as Tier 1 capital, period two	10 years
VNB Capital Trust I [Member]
Schedule Of Outstanding Junior Subordinated Debentures And The Related Trust Preferred Securities Issued [Line Items]
Principal face amounts redeemed of junior subordinated debentures	10,300,000
VNB Capital Trust I [Member] | Subordinated Debentures Subject to Mandatory Redemption [Member]
Schedule Of Outstanding Junior Subordinated Debentures And The Related Trust Preferred Securities Issued [Line Items]
Junior subordinated debentures issued to capital trusts	147,595,000	[1]	160,500,000
Contractual principal balances	146,715,000		157,000,000
VNB Capital Trust I [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member]
Schedule Of Outstanding Junior Subordinated Debentures And The Related Trust Preferred Securities Issued [Line Items]
Face value	142,313,000		152,300,000
Principal face amounts redeemed of junior subordinated debentures	10,000,000
GCB Capital Trust III [Member] | Subordinated Debentures Subject to Mandatory Redemption [Member]
Schedule Of Outstanding Junior Subordinated Debentures And The Related Trust Preferred Securities Issued [Line Items]
Junior subordinated debentures issued to capital trusts	25,051,000	[1]	25,100,000
Contractual principal balances	24,743,000		24,700,000
GCB Capital Trust III [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member]
Schedule Of Outstanding Junior Subordinated Debentures And The Related Trust Preferred Securities Issued [Line Items]
Face value	$ 24,000,000		$ 24,000,000

[1] The carrying value for GCB Capital Trust II includes an unamortized purchase accounting premium of $308 thousand, and the carrying values for State Bancorp Capital Trust I and State Bancorp Capital Trust II include purchase accounting discounts of $2.0 million and $2.8 million, respectively.