Consolidated Statements of Shareholders' Equity (USD $) In Thousands, except Share data	Total	Common Stock [Member]	Capital Surplus [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Deferred Compensation [Member]	Accumulated Other Comprehensive Earnings [Member]
Beginning Balance at Dec. 31, 2012	$ 556,963	$ 315	$ 277,412	$ 227,927	$ (5,007)	$ 5,007	$ 51,309
Beginning Balance, shares at Dec. 31, 2012		31,496,881			(266,845)
Net earnings (unaudited)	38,067			38,067
Stock issued in acquisition of Orange Savings Bank, SSB (unaudited)	23,100	4	23,096
Stock issued in acquisition of Orange Savings Bank, SSB, shares (unaudited)		420,000
Stock option exercises (unaudited)	1,260	1	1,259
Stock option exercises, shares (unaudited)		50,543
Cash dividends declared $0.27 per share (unaudited)	(16,190)			(16,190)
Change in unrealized gain in investment securities available-for-sale, net of related income taxes (unaudited)	(27,532)						(27,532)
Additional tax benefit related to directors' deferred compensation plan (unaudited)	20		20
Shares purchased in connection with directors' deferred compensation plan, net (unaudited)	0				(252)	252
Shares purchased in connection with directors' deferred compensation plan, net, shares (unaudited)					(2,734)
Stock option expense (unaudited)	176		176
Ending Balance (unaudited) at Jun. 30, 2013	575,864	320	301,963	249,804	(5,259)	5,259	23,777
Ending Balance, shares (unaudited) at Jun. 30, 2013		31,967,424			(269,579)
Beginning Balance at Dec. 31, 2013	587,647	320	302,991	273,972	(5,490)	5,490	10,364
Beginning Balance, shares at Dec. 31, 2013		31,992,497			(269,467)
Net earnings (unaudited)	43,541			43,541
Stock option exercises (unaudited)	910		910
Stock option exercises, shares (unaudited)		37,753
Cash dividends declared $0.27 per share (unaudited)	(17,291)			(17,291)
Change in unrealized gain in investment securities available-for-sale, net of related income taxes (unaudited)	24,822						24,822
Additional tax benefit related to directors' deferred compensation plan (unaudited)	50		50
Shares purchased in connection with directors' deferred compensation plan, net (unaudited)	0				(233)	233
Shares purchased in connection with directors' deferred compensation plan, net, shares (unaudited)					2,696
Stock option expense (unaudited)	357		357
Two-for-one stock split in the form of a 100% stock dividend (unaudited)	0	320		(320)
Two-for-one stock split in the form of a 100% stock dividend, shares (unaudited)		32,022,760			(268,134)
Ending Balance (unaudited) at Jun. 30, 2014	$ 640,036	$ 640	$ 304,308	$ 299,902	$ (5,723)	$ 5,723	$ 35,186
Ending Balance, shares (unaudited) at Jun. 30, 2014		64,053,010			(534,905)