Consolidated Balance Sheets (Parenthetical) (unaudited) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Consolidated Balance Sheets [Abstract]
Interest bearing deposits, banks	$ 56,571	$ 33,889
Held-to-maturity securities, fair value	$ 624,627	$ 639,273
Preferred stock, par value
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares outstanding
Common stock, par value	$ 2.0833	$ 2.0833
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	29,214,018	29,214,660
Common stock, shares outstanding	29,214,018	29,214,660
Treasury stock, shares	0	0