Commitments and Contingencies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Lease expiration date	Through 2058
Net rental expense	$ 23,800,000	$ 21,200,000	$ 21,100,000
Net of rental income	2,500,000	1,800,000	2,100,000
Maturity date, derivative instrument	Jul. 15, 2015
Total interest rate swaps aggregate notional amount	146,900,000
Aggregate notional amount of mortgage banking derivatives	194,300,000
Aggregate fair value of net liability position	26,200,000
Collateral posted with counterparties	25,900,000
Interest rate swaps [Member]
Notional amount of interest rate derivatives	300,000,000
Gain (loss) on cash flow hedge ineffectiveness	20,000	(32,000)
Accumulated net after-tax losses related to effective cash flow hedges	12,700,000	13,100,000
Estimated amount of interest rate derivatives to be reclassified to interest expense	8,600,000
Recognized a net reduction to interest expense	561,000	472,000
Interest rate caps [Member]
Gain (loss) on cash flow hedge ineffectiveness	73,000	(23,000)	(205,000)
State Bancorp, Inc.[Member]
Total interest rate swaps aggregate notional amount	16,400,000
Customer repurchase agreements and money market deposit accounts [Member] | Interest rate swaps starting July 12 2012 [Member]
Aggregate notional amount of interest rate derivative	100,000,000
Customer repurchase agreements and money market deposit accounts [Member] | Interest rate swaps due July 15, 2015 [Member]
Aggregate notional amount of interest rate derivative	100,000,000
Derivatives designated as hedging Instruments [Member] | Consumer and commercial money market deposit accounts [Member] | Interest rate swaps [Member]
Notional amount of interest rate derivatives	8,800,000
Derivatives designated as hedging Instruments [Member] | Consumer and commercial money market deposit accounts [Member] | Interest rate swaps [Member] | Fixed-rate at approximately 4.73% [Member]
Aggregate notional amount of interest rate derivative	200,000,000
Maturity date, derivative instrument	Oct. 01, 2016
Fixed interest rate	4.73%
Interest rate swap, starting date	July 2012
Derivatives designated as hedging Instruments [Member] | Consumer and commercial money market deposit accounts [Member] | Interest rate swaps [Member] | Fixed-rate at approximately 5.11% [Member]
Maturity date, derivative instrument	Jul. 01, 2017
Fixed interest rate	5.11%
Derivatives designated as hedging Instruments [Member] | Consumer and commercial money market deposit accounts [Member] | Interest rate caps [Member] | Minimum [Member]
Strike rates	6.00%
Derivatives designated as hedging Instruments [Member] | Consumer and commercial money market deposit accounts [Member] | Interest rate caps [Member] | Maximum [Member]
Strike rates	6.25%
Derivatives designated as hedging Instruments [Member] | Customer repurchase agreements and money market deposit accounts [Member] | Interest rate swaps [Member] | Fixed-rate at approximately 4.73% [Member]
Notional amount of interest rate derivatives	51,000,000
Maturity date, derivative instrument	Mar. 01, 2014
Derivatives designated as hedging Instruments [Member] | Customer repurchase agreements and money market deposit accounts [Member] | Interest rate swaps due May 1, 2013 [Member]
Aggregate notional amount of interest rate derivative	$ 100,000,000
Derivatives designated as hedging Instruments [Member] | Customer repurchase agreements and money market deposit accounts [Member] | Interest rate caps [Member]
Maturity date, derivative instrument	May 01, 2013
Derivatives designated as hedging Instruments [Member] | Customer repurchase agreements and money market deposit accounts [Member] | Interest rate caps [Member] | Minimum [Member]
Strike rates	2.50%
Derivatives designated as hedging Instruments [Member] | Customer repurchase agreements and money market deposit accounts [Member] | Interest rate caps [Member] | Maximum [Member]
Strike rates	2.75%