Consolidated Statements of Changes in Stockholders' Equity (USD $) In Thousands, except Share data	Total	Common Stock	Capital Surplus	Retained Earnings	Accumulated Other Comprehensive income (loss)
Beginning Balance at Dec. 31, 2010	$ 856,548	$ 122,855	$ 263,484	$ 470,828	$ (619)
Beginning Balance, Shares at Dec. 31, 2010		36,893,276
Net income	57,793			57,793
Other comprehensive income	34,793				34,793
Cash dividends declared ($0.72 per common share)	(50,051)			(50,051)
Common stock offering	213,994	23,170	190,824
Common stock offering, Shares		6,958,143
Common stock issued in connection with Whitney acquisition	1,308,044	135,845	1,172,199
Common stock issued in connection with Whitney acquisition, Shares		40,794,261
Common stock activity, long-term incentive plan, including excess income tax benefit of $92	5,541	175	5,366
Common stock activity, long-term incentive plan, including excess income tax benefit of $92, Shares		52,566
Ending Balance at Sep. 30, 2011	2,426,662	282,045	1,631,873	478,570	34,174
Ending Balance, Shares at Sep. 30, 2011		84,698,246
Beginning Balance at Dec. 31, 2011	2,367,163	282,069	1,634,634	476,970	(26,510)
Beginning Balance, Shares at Dec. 31, 2011		84,705,496
Net income	104,783			104,783
Other comprehensive income	14,723				14,723
Cash dividends declared ($0.72 per common share)	(61,915)			(61,915)
Common stock activity, long-term incentive plan, including excess income tax benefit of $92	9,734	254	9,480
Common stock activity, long-term incentive plan, including excess income tax benefit of $92, Shares		76,398
Ending Balance at Sep. 30, 2012	$ 2,434,488	$ 282,323	$ 1,644,114	$ 519,838	$ (11,787)
Ending Balance, Shares at Sep. 30, 2012		84,781,894