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 (Losses) [Member]
Beginning Balance at Dec. 31, 2011	$ 508,537	$ 314	$ 276,127	$ 184,871	$ (4,597)	$ 4,597	$ 47,225
Beginning Balance, Shares at Dec. 31, 2011		31,459,635			(258,235)
NET EARNINGS	74,225			74,225
Stock option exercises	825	1	824
Stock option exercises, Shares		37,246
Cash dividends declared	(31,169)			(31,169)
Minimum liability pension adjustment, net of related income taxes	(1,017)						(1,017)
Change in unrealized gain (loss) on investment insecurities available-for-sale, net of related income taxes	5,101						5,101
Additional tax benefit related to directors' deferred compensation plan	127		127
Shares purchased in connection with directors' deferred compensation plan, net					(410)	410
Shares purchased in connection with directors' deferred compensation plan, net, Shares					(8,610)
Stock option expense	334		334
Ending Balance at Dec. 31, 2012	556,963	315	277,412	227,927	(5,007)	5,007	51,309
Ending Balance, Shares at Dec. 31, 2012		31,496,881			(266,845)
NET EARNINGS	78,868			78,868
Stock issued in acquisition of Orange Savings Bank, SSB	23,100	4	23,096
Stock issued in acquisition of Orange Savings Bank, SSB, Shares		420,000
Stock option exercises	1,958	1	1,957
Stock option exercises, Shares		75,616
Cash dividends declared	(32,823)			(32,823)
Minimum liability pension adjustment, net of related income taxes	4,036						4,036
Change in unrealized gain (loss) on investment insecurities available-for-sale, net of related income taxes	(44,981)						(44,981)
Additional tax benefit related to directors' deferred compensation plan	115		115
Shares purchased in connection with directors' deferred compensation plan, net					(483)	483
Shares purchased in connection with directors' deferred compensation plan, net, Shares					(2,622)
Stock option expense	411		411
Ending Balance at Dec. 31, 2013	587,647	320	302,991	273,972	(5,490)	5,490	10,364
Ending Balance, Shares at Dec. 31, 2013		31,992,497			(269,467)
NET EARNINGS	89,559			89,559
Stock option exercises	1,437	1	1,436
Stock option exercises, Shares		74,664
Cash dividends declared	(35,233)			(35,233)
Minimum liability pension adjustment, net of related income taxes	1,651						1,651
Change in unrealized gain (loss) on investment insecurities available-for-sale, net of related income taxes	35,474						35,474
Additional tax benefit related to directors' deferred compensation plan	293		293
Shares purchased in connection with directors' deferred compensation plan, net					(388)	388
Shares purchased in connection with directors' deferred compensation plan, net, Shares					8,038
Stock option expense	709		709
Two-for-one stock split in the form of 100% stock dividend		320		(320)
Two-for-one stock split in the form of a 100% stock dividend, Shares		32,022,760			(268,134)
Ending Balance at Dec. 31, 2014	$ 681,537	$ 641	$ 305,429	$ 327,978	$ (5,878)	$ 5,878	$ 47,489
Ending Balance, Shares at Dec. 31, 2014		64,089,921			(529,563)