Business Combinations (Narrative) (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2012	Dec. 31, 2011
Business Acquisition [Line Items]
Acquisition date	January 1, 2012
Assets	$ 15,950,054,000	$ 14,244,507,000
Exchange ratio for one common stock	1
Fixed Rate Cumulative Series A Preferred Stock redeemed, value	36,800,000
Short-term loan for stock redemption	37,000,000
Debentures, maturity date	Nov. 07, 2032
Trust preferred securities, maturity date	Jan. 23, 2034
Assumed junior subordinated debentures	192,214,000	185,598,000
Number of years purchase warrant can be used	10
Number of common stock issued upon exercise of warrant	489,000
Exercise price of warrants	11.30
Merger expenses	980,000
Estimated useful life	11
State Bancorp Inc [Member]
Business Acquisition [Line Items]
Assets		1,700,000,000
Number of branches		16
Number of shares issued in acquisition	17,700,000
Total estimated consideration for the acquisition	208,400,000
Assumed junior subordinated debentures	$ 20,600,000
Short-Term Borrowings [Member]
Business Acquisition [Line Items]
Debentures, maturity date	Mar. 01, 2012