Assets Acquired and Liabilities Assumed in Acquisition Estimated Fair Values (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Business Acquisition [Line Items]
Junior subordinated debentures issued to capital trusts	$ 15,645
Other liabilities		51,312
Total liabilities assumed		1,476,250
Common stock issued in acquisition	208,418	208,418
State Bancorp, Inc.
Business Acquisition [Line Items]
Cash and cash equivalents		117,587
Investment securities available for sale		275,650
Loans		1,098,948
Premises and equipment		9,457
Accrued interest receivable		5,294
Goodwill		101,967
Other intangible assets		8,050
Other assets		67,715
Total assets acquired		1,684,668
Non-interest bearing		371,151
Savings, NOW and money market		596,599
Time		412,543
Total deposits		1,380,293
Short-term borrowings		29,000
Junior subordinated debentures issued to capital trusts		$ 15,645