Derivative Instruments and Hedging Activities - Additional Information (Detail) (USD $)	3 Months Ended	9 Months Ended	3 Months Ended		9 Months Ended				9 Months Ended			3 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended			6 Months Ended						9 Months Ended
	Sep. 30, 2012	Sep. 30, 2012	Sep. 30, 2012 Designated as Hedging Instrument	Sep. 30, 2011 Designated as Hedging Instrument	Sep. 30, 2012 Designated as Hedging Instrument	Sep. 30, 2011 Designated as Hedging Instrument	Sep. 30, 2012 Designated as Hedging Instrument Fixed Rate At Approximately 4.73%	Sep. 30, 2012 Designated as Hedging Instrument Fixed Rate At Approximately 5.11%	Sep. 30, 2012 Interest Rate Swap	Dec. 31, 2011 Interest Rate Swap	Sep. 30, 2012 Interest Rate Swap Not Designated as Hedging Instrument	Sep. 30, 2012 Interest Rate Swap Designated as Hedging Instrument	Sep. 30, 2011 Interest Rate Swap Designated as Hedging Instrument	Sep. 30, 2012 Interest Rate Swap Designated as Hedging Instrument	Sep. 30, 2011 Interest Rate Swap Designated as Hedging Instrument	Sep. 30, 2011 Interest Rate Cap	Sep. 30, 2012 Interest Rate Cap	Sep. 30, 2011 Interest Rate Cap	Sep. 30, 2012 State Bancorp, Inc. Interest Rate Swap Not Designated as Hedging Instrument	Sep. 30, 2012 Consumer Repurchase Agreements and Money Market Deposit Accounts Interest Rate Cap Designated as Hedging Instrument	Sep. 30, 2012 Consumer Repurchase Agreements and Money Market Deposit Accounts Interest Rate Cap Minimum Designated as Hedging Instrument	Sep. 30, 2012 Consumer Repurchase Agreements and Money Market Deposit Accounts Interest Rate Cap Maximum Designated as Hedging Instrument	Sep. 30, 2012 Consumer and Commercial Money Market Deposit Accounts Interest Rate Swap Designated as Hedging Instrument	Sep. 30, 2012 Consumer and Commercial Money Market Deposit Accounts Interest Rate Swap Minimum Designated as Hedging Instrument	Sep. 30, 2012 Consumer and Commercial Money Market Deposit Accounts Interest Rate Swap Maximum Designated as Hedging Instrument	Sep. 30, 2012 Consumer and Commercial Money Market Deposit Accounts Interest Rate Cap Designated as Hedging Instrument	Sep. 30, 2012 Consumer and Commercial Money Market Deposit Accounts Interest Rate Cap Minimum Designated as Hedging Instrument	Sep. 30, 2012 Consumer and Commercial Money Market Deposit Accounts Interest Rate Cap Maximum Designated as Hedging Instrument	Sep. 30, 2012 Commercial Loan Interest Rate Swap Designated as Hedging Instrument	Sep. 30, 2012 Certificates of Deposit Interest Rate Swap Designated as Hedging Instrument	Sep. 30, 2012 Certificates of Deposit Consumer and Commercial Money Market Deposit Accounts Interest Rate Swap Designated as Hedging Instrument Fixed Rate At Approximately 4.73%	Sep. 30, 2012 Certificates of Deposit Consumer and Commercial Money Market Deposit Accounts Interest Rate Swap Designated as Hedging Instrument Fixed Rate At Approximately 5.11%
Derivative [Line Items]
Aggregate notional amount of interest rate derivatives																				$ 100,000,000			$ 300,000,000			$ 100,000,000
Notional amount of interest rate derivatives							200,000,000	100,000,000			137,500,000								16,800,000										8,800,000	51,000,000
Fixed interest rate																								4.73%
Interest rate of swaps																									5.11%
Interest rate swap, starting date																																July 2012
Interest rate swap, expiration date																														March 2014	October 2016	July 2017
Strike rate																					2.50%	2.75%					6.00%	6.25%
Maturity date, derivative instrument																				May 1, 2013						July 15, 2015
Derivative instruments held											35								13
Mortgage banking derivatives, aggregate notional amount	331,200,000	331,200,000
Gain (loss) on cash flow hedge ineffectiveness																116,000	73,000	81,000
Accumulated net after-tax loss related to effective cash flow hedges									13,800,000	13,100,000
Estimated amount of interest rate derivatives to be reclassified to interest expense									6,700,000
Reduction to interest expense, net												141,000	146,000	416,000	332,000
Derivative instruments, gain (loss) designated as hedges	682,000	899,000	57,000	706,000	178,000	764,000
Aggregate fair value of net liability position	28,000,000	28,000,000
Collateral posted with counterparties	$ 25,700,000	$ 25,700,000