Acquisition Activity (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	May 31, 2011
Omni Bancshares, Inc. [Member]
Business Acquisition [Line Items]
Goodwill	$ 63,974,000	$ 63,974,000
Business acquisition, contingent consideration	46,407,000	46,407,000
Number of branch offices of acquiree	14
Operational days subsequent to acquisition	214
Purchase consideration paid	4,841,000
Acquisition date	5/31/2011
Additional goodwill	456,000
Cameron Bancshares, Inc. [Member]
Business Acquisition [Line Items]
Goodwill	71,557,000
Business acquisition, contingent consideration	143,241,000	143,241,000
Number of branch offices of acquiree	22
Operational days subsequent to acquisition	214
Number of ATMs		48
Purchase consideration paid	3,154,000
Acquisition date	5/31/2011
Additional goodwill	20,242,000
Florida Corporation [Member]
Business Acquisition [Line Items]
Goodwill	52,000
Purchase consideration paid	700,000
Contingent payment for the acquisition of assets	700,000
Resulted additional intangible assets included in Company's consolidated balance sheet	$ 1,400,000