Business Combination - Assets Acquired and Liabilities Assumed in Acquisition Estimated Fair Values (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Liabilities assumed:
Other liabilities		$ 52,998
Total liabilities assumed		1,477,936
Common stock issued in acquisition	208,418	208,418
State Bancorp, Inc.[Member]
Assets acquired:
Cash and cash equivalents		117,587
Investment securities available for sale		275,650
Loans		1,088,421
Premises and equipment		9,457
Accrued interest receivable		5,294
Goodwill		109,758
Other intangible assets		8,050
Other assets		72,137
Total assets acquired		1,686,354
Liabilities assumed:
Non-interest bearing deposits		371,151
Savings, NOW and money market deposits		596,599
Time deposits		412,543
Total deposits		1,380,293
Short-term borrowings		29,000
Junior subordinated debentures issued to capital trusts		$ 15,645